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NEET Biology Class 12 - Principles of Inheritance and Variation Ultra-Hard Question Bank

Duration: 230 minutesTotal Marks: 920Questions: 230Negative Marking: -1

Instructions:

  1. Each question has four options (1), (2), (3), (4). Choose the most correct answer.
  2. Each correct answer carries 4 marks.
  3. Each wrong answer will deduct 1 marks.
  4. Unanswered questions will not be penalised.
1.Assertion (A): James Dewey Watson received his Ph.D. degree in 1950 for his research on
the effect of hard X-rays on bacteriophage multiplication.

Reason (R): Watson received a Fellowship for graduate study in Zoology at Indiana University,
Bloomington, immediately after obtaining his B.Sc. degree in Zoology in 1947.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
2.Consider the following statements regarding Francis Harry Compton Crick as stated in the
NCERT biography:

I. He studied physics at University College, London and obtained a B.Sc. in 1937.

II. He completed his Ph.D. in 1954 on a thesis entitled 'X-ray Diffraction: Polypeptides and
Proteins'.

III. A critical influence in Crick's career was his friendship with J.D. Watson, who was a young
man of 25 when they proposed the double-helical structure of DNA.

IV. Crick was made a Fellow of the Royal Society (F.R.S.) in 1959.
Which of the combinations represents ONLY CORRECT statements?
(1)I, II, and IV
(2)I, II, and III
(3)All of the above
(4)II, III, and IV
3.Assertion (A): Watson and Crick received the John Collins Warren Prize of the
Massachusetts General Hospital in 1959, and the Lasker Award in 1960.

Reason (R): They were awarded the Nobel Prize in 1962, in the same year they received the
Research Corporation Prize.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
4.Regarding the discovery of the double helix structure of DNA, which of the following
statements is/are CORRECT according to NCERT?

I. Watson and Crick's first serious effort to solve the structure was highly successful and
accepted by all.

II. Their second effort, based on more experimental evidence and better appreciation of nucleic
acid literature, was proposed in early March 1953.

III. The double-helical configuration they proposed was complementary in nature.

IV. They relied on X-ray diffraction data of polypeptides and proteins produced by Maurice
Wilkins and Rosalind Franklin.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)II and III
(4)II, III, and IV
5.Assertion (A): Humans knew from as early as 8000-1000 B.C. that one of the causes of
variation was hidden in sexual reproduction.

Reason (R): Early humans selectively bred ancestral wild cows to produce modern high-yielding
Indian breeds like the Sahiwal cows in Punjab.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
6.Regarding the knowledge of inheritance in ancient times, which of the following statements
is/are CORRECT according to NCERT?

I. Early humans exploited variations naturally present in wild populations of plants and
animals.

II. The Sahiwal cow is an Indian breed developed through artificial selection and domestication
from ancestral wild cows.

III. Our ancestors possessed a deep, highly advanced scientific understanding of the molecular
basis of inheritance and variation.

IV. Selective breeding programs were highly successful because the ancestors worked with pure
lines only.
Choose the correct option:
(1)I and II
(2)All of the above
(3)II and III
(4)I, II, and IV
7.Assertion (A): Gregor Mendel conducted hybridization experiments on garden peas for
seven years, from 1856 to 1863.

Reason (R): During his investigations, it was for the first time in the history of science that
statistical analysis and mathematical logic were applied to problems in chemistry.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
8.Gregor Mendel's investigations into inheritance patterns achieved high credibility and
pointed to general rules of inheritance because of which of the following reasons in NCERT?

I. His experiments had a very small, highly controlled sampling size.

II. Confirmation of his inferences was performed on successive generations of test plants.

III. He worked exclusively with animals, which are easier to breed.

IV. His results pointed to general rules rather than unsubstantiated ideas.
Choose the correct option:
(1)All of the above
(2)I, II, and IV
(3)II and IV
(4)II and III
9.Assertion (A): Mendel investigated characters in the garden pea plant that were manifested
as two opposing traits, such as tall or dwarf plants, and yellow or green seeds.

Reason (R): This discrete trait selection allowed him to set up a basic framework of rules
governing inheritance, which was immediately accepted by all contemporary scientists in 1865.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
10.What is/are the characteristic feature(s) of a 'true-breeding line' as described by Gregor
Mendel in the NCERT text?

I. Having undergone continuous self-pollination.

II. Having undergone continuous cross-pollination.

III. Shows stable trait inheritance and expression for several generations.

IV. Shows dynamic, high-rate mutations and trait variation across generations.
Choose the correct option:
(1)I and III
(2)II and IV
(3)I and IV
(4)II and III
11.Assertion (A): Mendel selected exactly 7 true-breeding pea plant varieties as pairs which
were similar except for one character with contrasting traits.

Reason (R): The 14 true-breeding pea plant varieties represented seven characters, each with
two contrasting traits studied by Mendel.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
12.Which of the following pairings of characters and their dominant/recessive traits studied
by Mendel is/are INCORRECT according to NCERT?

I. Pod colour: Dominant is Yellow, Recessive is Green.

II. Seed colour: Dominant is Yellow, Recessive is Green.

III. Pod shape: Dominant is Inflated, Recessive is Constricted.

IV. Flower position: Dominant is Terminal, Recessive is Axial.
Choose the correct option:
(1)I, II, and IV
(2)I and IV
(3)I, III, and IV
(4)II and III
13.Assertion (A): Flower colour violet is dominant over white flower colour, and constricted
pod shape is recessive to inflated pod shape.

Reason (R): Mendel studied flower colour and pod shape as two of the seven character pairs in
his hybridization experiments.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
14.Gregor Mendel studied seven characters in garden peas. Which of the following represents
the exact list of the 7 characters (not traits) studied by him?

I. Stem height and Flower colour.

II. Flower position and Pod shape.

III. Pod colour and Seed shape.

IV. Seed colour and Pod height.
Choose the correct option:
(1)All of the above
(2)I, II, and IV
(3)II, III, and IV
(4)I, II, and III
15.Assertion (A): In Mendel's pea plant varieties, round seed shape is dominant over
wrinkled, and green seed colour is recessive to yellow seed colour.

Reason (R): Green seed colour is dominant in pod colour, showing that green pigment
expression is always dominant in all organs of the pea plant.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
16.Mendel crossed tall and dwarf pea plants to study monohybrid inheritance. Which of the
following observations regarding the F1 generation is/are CORRECT according to NCERT?

I. All the F1 progeny plants were tall; none were dwarf.

II. The F1 progeny plants showed intermediate height between the tall and dwarf parents.

III. The F1 generation always resembled either one of the parents.

IV. The trait of the other parent (dwarf) was not seen in the F1 generation.
Choose the correct option:
(1)I and III only
(2)I, III, and IV
(3)II and IV
(4)All of the above
17.Assertion (A): When Mendel self-pollinated the tall F1 plants, he observed that 1/4th of the
F2 plants were dwarf and 3/4th were tall.

Reason (R): The tall and dwarf traits in the F2 generation showed significant blending, resulting
in 50% of the plants having an in-between height.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
18.Regarding Mendel's monohybrid crosses for all seven character pairs, which of the
following statements are CORRECT according to NCERT?

I. Only one of the parental traits was expressed in the F1 generation.

II. Both contrasting traits were expressed at the F2 stage.

III. The F2 expression of the recessive trait occurred in the proportion of 1/4th.

IV. The contrasting traits showed minor blending at the F2 stage due to environmental factors.
Choose the correct option:
(1)II, III, and IV
(2)All of the above
(3)I, II, and III
(4)I and II only
19.Assertion (A): Mendel proposed that 'factors' are stably passed down, unchanged, from
parent to offspring through the gametes, over successive generations.

Reason (R): We now call these factors as alleles, which contain the information required to
express a particular trait in an organism.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
20.Which of the following statements regarding genes and alleles is/are CORRECT according
to NCERT?

I. Genes contain the information that is required to express a particular trait in an organism.

II. Alleles are slightly different forms of the same gene.

III. Alleles are completely different genes located on different chromosomes.

IV. Genes which code for a pair of contrasting traits are known as alleles.
Choose the correct option:
(1)All of the above
(2)I and II only
(3)I, II, and IV
(4)II, III, and IV
21.Assertion (A): Capital letter T is used for the tall trait expressed at the F1 stage, and
lowercase t is used for the dwarf trait that is recessive.

Reason (R): It is convenient to use the capital and lower case of an alphabetical symbol because
it helps us remember that they are alleles of the same gene.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
22.Gregor Mendel defined genotype and phenotype for height. Which of the following
statements is/are CORRECT according to NCERT?

I. TT and tt are homozygous genotypic states for height.

II. Genotype represents the descriptive terms like 'tall' and 'dwarf'.

III. Phenotype represents the allelic pairs of genes, such as TT, Tt, or tt.

IV. A heterozygous plant with genotype Tt has a 'tall' phenotype.
Choose the correct option:
(1)I and IV
(2)All of the above
(3)II and III
(4)I, II, and IV
23.Assertion (A): In a heterozygous tall plant (Tt), the factor 'T' dominates the other factor 't',
which is therefore called dominant.

Reason (R): Dissimilar factors in a pair always express their traits equally in the heterozygote,
resulting in a hybrid that is a perfect blend of both parents.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
24.Regarding the meiotic segregation of alleles during gametogenesis in pea plants, which of
the following statements are CORRECT?

I. The separation of alleles of a parental pair occurs by the process of mitosis.

II. Segregation of alleles is a random process with a 50 percent chance of a gamete containing
either allele.

III. The recessive parental trait is expressed with significant blending in the F2 generation.

IV. Zygotes are formed when the alleles from the pollen and egg unite during fertilization.
Choose the correct option:
(1)I, II, and IV
(2)II and IV
(3)All of the above
(4)II and III
25.Assertion (A): The Punnett Square is a graphical representation used to calculate the
probability of all possible genotypes of offspring in a genetic cross.

Reason (R): The Punnett Square was developed by a famous British geneticist named Reginald
C. Punnett.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
26.Which of the following descriptions represents the CORRECT layout and symbols of a
Punnett Square according to NCERT?

I. The possible gametes are written on two sides, usually the top row and left columns.

II. All possible combinations of zygotes are represented in boxes below, generating a square
output form.

III. The symbol ⚥ is used exclusively to denote the self-pollinating hermaphrodite state.

IV. The symbols ♀ and ♂ are used to denote the female and male parental gametes respectively.
Choose the correct option:
(1)I, II, and IV
(2)I and II only
(3)All of the above
(4)II, III, and IV
27.Assertion (A): The gametes of the heterozygous tall Tt plants contain both the T and t
alleles in equal, unseparated proportions within a single gamete.

Reason (R): Segregation is a random process, ensuring that the probability of a pollen or egg
containing either allele is exactly 50 percent.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
28.Mendel selected 14 true-breeding pea plant varieties representing 7 contrasting character
pairs. Which of the following is/are CORRECT examples of recessive traits studied by him?

I. Constricted pod shape and Yellow pod colour.

II. Green seed colour and White flower colour.

III. Terminal flower position and Dwarf stem height.

IV. Wrinkled seed shape and Inflated pod shape.
Choose the correct option:
(1)I and II only
(2)II, III, and IV
(3)I, II, and III
(4)All of the above
29.Assertion (A): Mendel investigated characters in the garden pea plant that were
manifested as two opposing traits, which made his genetic framework highly simple and clear.

Reason (R): This discrete opposing trait framework completely prevented any biological
complexity or exceptions, ensuring that all genes in nature follow complete dominance.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
30.Gregor Mendel conducted artificial pollination and cross-pollination experiments. Which
of the following steps is/are CORRECT regarding his crossing technique according to NCERT
Figure 4.2?

I. Emasculation involves the removal of anthers from the female parent flower before they
dehisce.

II. Emasculation is performed on both the male and female parent flowers simultaneously.

III. Pollen grains collected from the male parent are transferred to the stigma of the
emasculated female flower.

IV. The crossed flowers are left completely open to the air to facilitate natural insect pollination.
Choose the correct option:
(1)All of the above
(2)II and IV
(3)I and III
(4)I, II, and III
31.Assertion (A): The meiotic segregation of alleles in the F1 heterozygote Tt leads to a
mathematically predictable 1:2:1 ratio of TT, Tt, and tt in the F2 generation.

Reason (R): The Punnett Square calculations are based on binomial expansion (ax + by)^2,
where the frequency of alleles T and t are represented by p and q respectively, giving (p + q)^2 =
p^2 + 2pq + q^2 = 1.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
32.Regarding Gregor Mendel's test cross, which of the following statements are CORRECT
according to NCERT?

I. A test cross is performed by crossing a plant showing dominant phenotype with a homozygous
recessive parent.

II. A test cross is performed by crossing a plant showing recessive phenotype with a homozygous
dominant parent.

III. The purpose of a test cross is to determine the unknown genotype of a dominant phenotypic
plant.

IV. In a typical test cross of a monohybrid, the expected phenotypic ratio of the offspring is 3:1.
Choose the correct option:
(1)II, III, and IV
(2)II and III
(3)I and III
(4)I, III, and IV
33.Assertion (A): In a test cross of a violet-flowered pea plant of unknown genotype, if all the
resulting offspring are violet-flowered, the parent is homozygous dominant.

Reason (R): In a test cross of a heterozygous violet-flowered plant (Ww) with a white-flowered
plant (ww), 50% of the offspring will be white-flowered and 50% will be violet-flowered.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
34.Regarding the genetics of incomplete dominance in snapdragon (Antirrhinum majus),
which of the following statements is/are CORRECT according to NCERT?

I. The cross between true-breeding red-flowered (RR) and true-breeding white-flowered (rr)
plants yields pink-flowered (Rr) F1 offspring.

II. Selfing the pink F1 plants yields an F2 phenotypic ratio of 3 Red : 1 White.

III. The F2 genotypic and phenotypic ratios in snapdragon are exactly identical, both being
1:2:1.

IV. Pink flower colour represents a case of incomplete dominance because there is blending of
alleles at the genotypic level.
Choose the correct option:
(1)II, III, and IV
(2)I and III
(3)I, II, and III
(4)All of the above
35.Assertion (A): In the cross of snapdragon plants, the classic Mendelian F2 monohybrid
phenotypic ratio of 3:1 is modified to a 1:2:1 ratio.

Reason (R): The allele R is completely dominant over the allele r, ensuring that heterozygotes
(Rr) express the exact same phenotype as the homozygous dominant parent (RR).
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
36.Regarding the concept of dominance and modified alleles, which of the following
statements is/are CORRECT according to NCERT?

I. The unmodified allele represents the original phenotype and is generally the dominant allele.

II. The modified allele is generally the recessive allele because it produces a non-functional
enzyme or no enzyme at all.

III. If the modified allele produces a normal or less efficient enzyme, it will produce the same
phenotype as the unmodified allele.

IV. The transformation of a diploid cell involves the modification of all genes on all
chromosomes simultaneously.
Choose the correct option:
(1)All of the above
(2)II, III, and IV
(3)I, II, and III
(4)I and II only
37.Assertion (A): The phenotype of a heterozygous individual is dependent only on the
functioning of the modified allele in a diploid cell.

Reason (R): The modified allele is generally recessive because it leads to the production of a
non-functional enzyme or no enzyme, making the phenotype dependent on the functioning of
the unmodified allele.
(1)Option 2
(2)Option 4
(3)Option 1
(4)Option 3
38.Regarding the human ABO blood grouping system described in NCERT, which of the
following statements is/are CORRECT?

I. ABO blood groups are controlled by the gene I, which has three alleles: I^A, I^B, and i.

II. The plasma membrane of red blood cells has sugar polymers that protrude from its surface.

III. The kind of sugar polymer present on the RBC surface is determined by the specific allele of
gene I.

IV. Alleles I^A and I^B produce a slightly different form of the sugar, while allele i produces a
highly complex, modified sugar.
Choose the correct option:
(1)All of the above
(2)I and II only
(3)II, III, and IV
(4)I, II, and III
39.Assertion (A): When an individual has both I^A and I^B alleles, their red blood cells
express both A and B types of sugars.

Reason (R): The alleles I^A and I^B exhibit co-dominance, meaning both alleles are expressed
completely and equally in the heterozygous state.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
40.Regarding the genetics of multiple alleles in human ABO grouping, which of the following
statements is/are CORRECT according to NCERT?

I. Since there are three different alleles, a single diploid individual can possess all three alleles
simultaneously.

II. Multiple alleles can be found and studied only when population studies are made.

III. The total number of possible genotypes in the human population for ABO blood groups is
six.

IV. The total number of possible phenotypes (blood groups) in the human population is four.
Choose the correct option:
(1)I, II, and III
(2)II and IV only
(3)All of the above
(4)II, III, and IV
41.Assertion (A): There are six different genotypes and four different phenotypes in the
human population for ABO blood groups.

Reason (R): The allele i is recessive to both I^A and I^B, while alleles I^A and I^B are co-
dominant, allowing I^AI^B to express a unique phenotype.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
42.According to NCERT Table 4.2 showing genetic basis of blood groups, which of the
following crosses will yield offspring with ONLY ONE phenotype?

I. Homozygous A (I^AI^A) x Homozygous B (I^BI^B)

II. Homozygous A (I^AI^A) x O blood group (ii)

III. Heterozygous A (I^Ai) x Heterozygous B (I^Bi)

IV. AB blood group (I^AI^B) x O blood group (ii)
Choose the correct option:
(1)All of the above
(2)II and III
(3)I, II, and IV
(4)I and II
43.Assertion (A): Multiple alleles governing a character in a population are located at entirely
different loci across different chromosomes.

Reason (R): A diploid individual possesses only two chromosomes of a homologous pair and can
therefore represent only two alleles of a multiple allelic series.
(1)Option 1
(2)Option 2
(3)Option 4
(4)Option 3
44.In Mendel's monohybrid selfing of F1 (Tt) plants, which of the following represents the
CORRECT mathematical proportions of F2 genotypes according to NCERT?

I. The proportion of homozygous dominant tall plants (TT) is 1/4th.

II. The proportion of heterozygous tall plants (Tt) is 1/2.

III. The proportion of homozygous recessive dwarf plants (tt) is 1/4th.

IV. The proportion of phenotypically tall plants (TT and Tt combined) is 3/4th.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)I and III only
(4)II and IV only
45.Assertion (A): To determine the genotype of a tall F2 plant, Mendel self-pollinated it for
several successive generations.

Reason (R): Selfing a heterozygous tall plant (Tt) yields a 3:1 phenotypic ratio, whereas crossing
it with a homozygous recessive parent (tt) in a test cross yields a 1:1 ratio.
(1)Option 2
(2)Option 4
(3)Option 1
(4)Option 3
46.Regarding the model plant species used to study incomplete dominance, which of the
following descriptions is/are CORRECT according to NCERT?

I. The common name is snapdragon or dog flower.

II. The botanical scientific name is Antirrhinum majus.

III. The inheritance of flower colour in this species is a classic example of incomplete
dominance.

IV. The homozygous recessive state in this species yields pink flowers.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)I and II only
(4)II and III only
47.Assertion (A): Dominance is an autonomous, intrinsic feature of a gene or its product, and
is completely independent of the specific phenotype we choose to examine.

Reason (R): A single gene can influence more than one phenotypic trait, and the expression of
dominance can vary depending on which phenotype is chosen as the reference.
(1)Option 3
(2)Option 2
(3)Option 1
(4)Option 4
48.Which of the following statements regarding the concept of dominance is/are
CONSISTENT with NCERT?

I. Dominance is not an autonomous feature of a gene.

II. Dominance depends on the gene product and the production of a particular phenotype from
this product.

III. Dominance is an absolute, fixed property that is independent of the chosen phenotype.

IV. A gene product can lead to more than one phenotype, showing varying dominance behavior.
Choose the correct option:
(1)I, II, and IV
(2)I and II only
(3)II and III
(4)All of the above
49.Assertion (A): Mendel proposed that factors are stably passed down, unchanged, over
successive generations.

Reason (R): During gametogenesis, the pair of alleles undergo significant somatic crossing over,
resulting in the creation of blended alleles.
(1)Option 2
(2)Option 3
(3)Option 1
(4)Option 4
50.Regarding the meiotic segregation of alleles in a heterozygous plant (Tt), which of the
following is/are CORRECT according to NCERT?

I. The segregation of alleles is a completely random process.

II. There is a 25 percent chance of a gamete containing the dominant allele T.

III. There is a 50 percent chance of a gamete containing either allele.

IV. Pollen grains can contain both alleles T and t simultaneously due to incomplete cytokinesis.
Choose the correct option:
(1)I, II, and III
(2)II and IV
(3)I and III
(4)All of the above
51.Assertion (A): In snapdragon F2 progeny, the phenotypic ratio is 1 Red : 2 Pink : 1 White,
which matches the genotypic ratio of 1 RR : 2 Rr : 1 rr.

Reason (R): The pink flower colour is expressed by the homozygous dominant genotype RR due
to partial enzymatic activity.
(1)Option 4
(2)Option 1
(3)Option 2
(4)Option 3
52.The human ABO blood grouping system exhibits which of the following genetic
phenomena according to NCERT?

I. Complete Dominance.

II. Incomplete Dominance.

III. Co-dominance.

IV. Multiple Alleles.
Choose the correct option:
(1)I and III only
(2)I, III, and IV
(3)All of the above
(4)II, III, and IV
53.Assertion (A): The plasma membranes of human erythrocytes possess protruding sugar
polymers that are controlled by the gene I.

Reason (R): The alleles I^A and I^B catalyze the addition of slightly different forms of sugar,
whereas the allele i catalyzes the addition of a highly basic amino sugar.
(1)Option 4
(2)Option 1
(3)Option 2
(4)Option 3
54.How many different genotypes are possible in the human population for ABO blood
grouping, and what are their specific formulas according to NCERT?

I. There are exactly six different genotypes.

II. There are exactly four different genotypes.

III. The genotypes are represented by: I^AI^A, I^Ai, I^BI^B, I^Bi, I^AI^B, and ii.

IV. The genotypes are represented by: I^AI^A, I^AI^B, I^BI^B, and ii only.
Choose the correct option:
(1)II and IV
(2)I and IV
(3)II and III
(4)I and III
55.Assertion (A): Multiple alleles can be identified and studied only when large-scale
population studies are conducted.

Reason (R): An individual organism is diploid and can only carry a maximum of two alleles at a
given locus on homologous chromosomes.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
56.Which of the following describes the functional state of an 'unmodified allele' in a diploid
cell according to NCERT?

I. It represents the original, functional phenotype.

II. It produces a fully active, normal enzyme.

III. It behaves as a recessive allele when paired with a modified allele.

IV. It is generally the dominant allele in the heterozygous state.
Choose the correct option:
(1)All of the above
(2)II, III, and IV
(3)I and II only
(4)I, II, and IV
57.Assertion (A): When a modified allele produces a non-functional enzyme or no enzyme, the
phenotype is completely determined by the unmodified allele.

Reason (R): The modified allele in this state behaves as the dominant allele because it prevents
the unmodified allele from expressing its product.
(1)Option 4
(2)Option 2
(3)Option 3
(4)Option 1
58.According to NCERT, the modified allele could theoretically be responsible for the
production of which of the following three enzyme outcomes?

I. A normal or less efficient enzyme.

II. A non-functional enzyme.

III. No enzyme at all.

IV. A highly active, hyper-functional enzyme.
Choose the correct option:
(1)All of the above
(2)I and II only
(3)II, III, and IV
(4)I, II, and III
59.Assertion (A): A test cross of a heterozygous violet-flowered pea plant (Ww) with a white-
flowered parent (ww) results in a 1:1 genotypic and phenotypic ratio.

Reason (R): The white-flowered parent is homozygous recessive (ww) and produces only one
type of gamete carrying the recessive allele w.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
60.A child has blood group O. Which of the following parental genotypes is/are
mathematically CAPABLE of producing this child according to NCERT Table 4.2?

I. Parent 1: Heterozygous A (I^Ai), Parent 2: Heterozygous B (I^Bi)

II. Parent 1: AB (I^AI^B), Parent 2: O (ii)

III. Parent 1: Homozygous A (I^AI^A), Parent 2: Homozygous B (I^BI^B)

IV. Parent 1: Heterozygous A (I^Ai), Parent 2: O (ii)
Choose the correct option:
(1)II and III
(2)I and IV
(3)All of the above
(4)I, II, and IV
61.Assertion (A): Crossing a pea plant with yellow-round seeds and a plant with green-
wrinkled seeds results in F1 offspring that all possess yellow-round seeds.

Reason (R): Yellow seed colour is dominant over green seed colour, and round seed shape is
dominant over wrinkled seed shape, showing complete dominance in the dihybrid F1
heterozygous state.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
62.Regarding the F2 generation of Mendel's dihybrid cross (Round-Yellow x Wrinkled-
Green), which of the following phenotypic combinations and their proportions are CORRECT
according to NCERT?

I. Round-Yellow represents 9/16th of the total progeny.

II. Wrinkled-Green represents 1/16th of the total progeny.

III. Wrinkled-Yellow represents 3/16th of the total progeny.

IV. Round-Green represents 3/16th of the total progeny.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)I and III only
(4)II and IV only
63.Assertion (A): The F2 dihybrid phenotypic ratio 9:3:3:1 is derived mathematically by
multiplying the individual monohybrid phenotypic ratios of 3:1 for each character pair.

Reason (R): In a dihybrid cross, the probability of seed shape and seed colour combinations is
computed as: (3 Round : 1 Wrinkled) x (3 Yellow : 1 Green) = 9 Round-Yellow : 3 Round-Green
: 3 Wrinkled-Yellow : 1 Wrinkled-Green.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
64.Gregor Mendel's Law of Independent Assortment is defined by which of the following
statements in NCERT?

I. When two pairs of traits are combined in a hybrid, segregation of one pair of characters is
independent of the other pair.

II. When two pairs of traits are combined in a hybrid, segregation of one pair of characters is
completely dependent on and linked to the other pair.

III. The law explains the F2 dihybrid ratio of 9:3:3:1 observed in garden peas.

IV. The law applies only to genes that are located on the exact same homologous chromosome in
close proximity.
Choose the correct option:
(1)I and III
(2)II and III
(3)I, III, and IV
(4)II, III, and IV
65.Assertion (A): During meiosis in a dihybrid plant (RrYy), the segregation of the gene pair
R/r is completely independent of the segregation of the gene pair Y/y.

Reason (R): The alleles R and r always segregate into the exact same gametes as the alleles Y
and y respectively, ensuring parental combinations are conserved.
(1)Option 4
(2)Option 1
(3)Option 3
(4)Option 2
66.In a dihybrid plant with genotype RrYy, what are the types and proportions of gametes
produced by meiosis according to NCERT?

I. The plant produces four different types of gametes: RY, Ry, rY, and ry.

II. Each of the four gametes represents exactly 25% (or 1/4th) of the total gametes produced.

III. The gamete types RY and ry represent 50% each of the total gametes, while recombinants
are absent.

IV. The segregation of 50% R and 50% r is independent of the segregation of 50% Y and 50% y.
Choose the correct option:
(1)II and IV only
(2)I, II, and III
(3)I, II, and IV
(4)I and III only
67.Assertion (A): The Punnett Square representation for a dihybrid self-pollination cross of
RrYy contains exactly 16 boxes.

Reason (R): The dihybrid heterozygote RrYy produces four types of male gametes and four
types of female gametes, and the grid size is: 4 imes 4 = 16.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
68.Gregor Mendel's laws of inheritance, published in 1865, remained unrecognized for 35
years until 1900. According to NCERT, which of the following is/are the CORRECT reasons for
this neglect?

I. Communication was not easy in those days, preventing wide publicity of his work.

II. His concept of genes (factors) as stable and discrete units was not accepted as it did not
account for continuous variation seen in nature.

III. His application of statistical analysis and mathematical logic was completely new and
unacceptable to contemporary biologists.

IV. Mendel was unable to provide physical proof for the existence of factors or show what they
were made of.
Choose the correct option:
(1)I and III only
(2)All of the above
(3)II and IV only
(4)I, II, and III
69.Assertion (A): In 1900, three scientists independently rediscovered Mendel's results on the
inheritance of characters.

Reason (R): These three scientists were Hugo de Vries, Carl Correns, and Erich von Tschermak.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
70.Which of the following advancements in the late nineteenth century facilitated the
rediscovery of Mendel's laws and the birth of cytogenetics according to NCERT?

I. Advancements in microscopy took place, allowing scientists to carefully observe cell division.

II. Scientists discovered double-stranded helical DNA in chromosomes using electron
microscopes.

III. Scientists observed structures in the nucleus that appeared to double and divide just before
cell division, which were called chromosomes.

IV. The discovery of transcription factors confirmed the presence of stable 'factors'.
Choose the correct option:
(1)II and IV
(2)All of the above
(3)I, II, and III
(4)I and III
71.Assertion (A): Walter Sutton and Theodore Boveri proposed the Chromosomal Theory of
Inheritance in 1902.

Reason (R): Sutton and Boveri noted that the behavior of chromosomes was parallel to the
behavior of genes and used chromosome movement to explain Mendel's laws.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
72.According to NCERT Table 4.3 comparing the behavior of chromosomes and genes, which
of the following is/are CORRECT features of BOTH columns?

I. Both genes and chromosomes occur in pairs in diploid cells.

II. Both genes and chromosomes segregate at the time of gamete formation such that only one of
each pair is transmitted to a gamete.

III. One pair of genes or chromosomes assorts independently of another pair.

IV. Independent assortment applies to genes only if they are located on non-homologous
chromosomes.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)II and IV only
(4)I and III only
73.Assertion (A): During Anaphase of Meiosis I, the two chromosome pairs can align at the
metaphase plate independently of each other.

Reason (R): The alignment of chromosomes at Metaphase I is a random process, ensuring that
the maternal and paternal chromosomes of different pairs distribute randomly into gametes.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
74.Walter Sutton and Theodore Boveri synthesized chromosomal behavior with Mendelian
laws. Which of the following parallel behaviors is/are CORRECT according to NCERT?

I. Genes occur in pairs, and homologous chromosomes also occur in pairs.

II. Alleles of a gene pair are located on non-homologous sites of homologous chromosomes.

III. Alleles of a gene pair are located on homologous sites on homologous chromosomes.

IV. Segregation of chromosome pairs leads directly to the independent segregation of the alleles
they carry.
Choose the correct option:
(1)I and II only
(2)I, III, and IV
(3)II, III, and IV
(4)All of the above
75.Assertion (A): Walter Sutton united the knowledge of chromosomal segregation with
Mendelian principles, creating the synthesis known as Chromosomal Theory of Inheritance.

Reason (R): Sutton was the first scientist to experimentally verify the chromosomal theory of
inheritance using Drosophila melanogaster as a model organism.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
76.In a standard Mendelian dihybrid F2 generation (selfing of RrYy), what is the total
number of different genotypes and different phenotypes observed according to NCERT?

I. There are exactly nine different genotypes.

II. There are exactly four different phenotypes.

III. The genotypes are represented in a 9:3:3:1 ratio.

IV. The phenotypes are represented in a 9:3:3:1 ratio.
Choose the correct option:
(1)II and IV only
(2)I and III only
(3)I, II, and III
(4)I, II, and IV
77.Assertion (A): In Mendel's dihybrid F2 generation, new recombinant phenotypes like
round-green and wrinkled-yellow seeds are recovered.

Reason (R): The genes controlling seed shape and seed colour are located on the same
chromosome and show tight physical linkage, preventing parental combination breakdown.
(1)Option 1
(2)Option 2
(3)Option 3
(4)Option 4
78.A plant has genotype RrYy. Under independent assortment, which of the following gamete
combinations is/are parental (non-recombinant) and which are recombinant?

I. RY and ry are parental gamete types.

II. Ry and rY are recombinant gamete types.

III. RY and Ry are parental, while rY and ry are recombinant gamete types.

IV. All four gametes RY, Ry, rY, and ry are parental gamete types.
Choose the correct option:
(1)I and II
(2)II and IV only
(3)I, II, and III
(4)I and III only
79.Assertion (A): Mendel's application of statistical analysis and mathematical logic was
initially completely ignored and rejected by contemporary biologists.

Reason (R): Biology in the nineteenth century was strictly qualitative, and the introduction of
mathematical logic to biological problems was entirely new and foreign to scientists of that era.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
80.In Mendel's dihybrid cross of Round-Yellow and Wrinkled-Green seeds, what were the
exact genotypes of the true-breeding parents according to NCERT?

I. Round-Yellow parent genotype was RRYY.

II. Wrinkled-Green parent genotype was rryy.

III. Round-Yellow parent genotype was RrYy.

IV. Wrinkled-Green parent genotype was Rryy.
Choose the correct option:
(1)I, II, and III
(2)I and IV
(3)II and IV
(4)I and II
81.Assertion (A): Thomas Hunt Morgan and his colleagues selected Drosophila melanogaster,
the common fruit fly, to experimentally verify the Chromosomal Theory of Inheritance.

Reason (R): Drosophila could be grown easily on simple synthetic medium in the laboratory,
had a short life cycle of about two weeks, and produced a large number of progeny from a single
mating.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
82.Which of the following is/are the CORRECT reason(s) for selecting Drosophila
melanogaster in Morgan's genetic experiments according to NCERT?

I. They could be grown on simple synthetic medium in the laboratory.

II. A single mating could produce a large number of progeny flies.

III. There was a clear differentiation of the sexes—the male and female flies are easily
distinguishable.

IV. It had many types of hereditary variations that could be seen with low-power microscopes.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV only
(4)I and III only
83.Assertion (A): T.H. Morgan crossed yellow-bodied, white-eyed females with brown-bodied,
red-eyed males to study the inheritance of X-linked genes in Drosophila.

Reason (R): In Drosophila, brown body and red eyes are the recessive traits, while yellow body
and white eyes are the dominant wild-type traits.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
84.Regarding the F2 generation of Morgan's Drosophila crosses, which of the following
statements is/are CORRECT according to NCERT?

I. The two genes did not segregate independently of each other, showing a significant deviation
from the Mendelian 9:3:3:1 ratio.

II. If two genes were located on the same chromosome, the proportion of parental gene
combinations was much higher than the non-parental type.

III. The F2 phenotypic ratio was exactly 9:3:3:1, showing complete agreement with the Law of
Independent Assortment.

IV. Parental combinations were completely absent in the F2 generation due to high crossing
over.
Choose the correct option:
(1)All of the above
(2)I, II, and IV
(3)I and II
(4)II and III
85.Assertion (A): Thomas Hunt Morgan coined the term 'linkage' to describe the physical
association of genes on a chromosome.

Reason (R): Morgan coined the term 'recombination' to describe the generation of non-parental
gene combinations during sexual reproduction.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
86.Morgan performed two dihybrid crosses in Drosophila (Cross A: yellow-white, Cross B:
white-miniature). Which of the following experimental results is/are CORRECT according to
NCERT?

I. Cross A (yellow and white genes) showed a recombinant frequency of exactly 1.3%.

II. Cross B (white and miniature wing genes) showed a recombinant frequency of exactly 37.2%.

III. The yellow and white genes in Cross A were much more tightly linked than the white and
miniature genes in Cross B.

IV. The parental combination frequency in Cross A was exactly 98.7%, and in Cross B was
exactly 62.8%.
Choose the correct option:
(1)I, II, and III
(2)I and III only
(3)All of the above
(4)II and IV only
87.Assertion (A): Genes that are located very close to each other on the same chromosome
show extremely low recombination frequencies.

Reason (R): The physical distance between two genes on a chromosome is inversely proportional
to their linkage strength, meaning closely situated genes are tightly linked.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
88.Regarding the development of genetic mapping as described in NCERT, which of the
following statements is/are CORRECT?

I. Alfred Sturtevant, a student of Thomas Hunt Morgan, developed the first genetic maps.

II. Sturtevant used the frequency of recombination between gene pairs on the same chromosome
as a measure of the distance between genes.

III. Recombination frequency was directly translated into map distance units to map positions
on the chromosome.

IV. Sturtevant used Drosophila polytene salivary gland chromosome staining to visually count
physical gene distances.
Choose the correct option:
(1)I, II, and III
(2)II, III, and IV
(3)I and II only
(4)All of the above
89.Assertion (A): Genetic maps are widely used today as a starting point in the sequencing of
whole genomes, such as in the Human Genome Project.

Reason (R): Sturtevant's mapping technique has been completely replaced by modern physical
sequencing, and genetic maps are no longer of any scientific value today.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
90.Thomas Hunt Morgan's experimental work accomplished which of the following
milestones in genetics according to NCERT?

I. Provided direct experimental verification of the Chromosomal Theory of Inheritance.

II. Disproved Mendel's laws of inheritance once and for all by showing they were completely
false.

III. Led to the discovery of the physical basis of variation during sexual reproduction.

IV. Proved that genes for all characters reside on separate non-homologous autosomes in
Drosophila.
Choose the correct option:
(1)I and III
(2)I, II, and III
(3)II and IV
(4)All of the above
91.Assertion (A): Walter Sutton argued that the pairing and segregation of a pair of
chromosomes would lead to the independent segregation of a pair of factors they carried.

Reason (R): Homologous chromosomes pair up and segregate during meiosis, which physically
carries the alleles situated on their homologous loci into separate gametes.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
92.By which year was the meiotic chromosome movement fully worked out cytologically,
leading to Boveri and Sutton's synthesis according to NCERT?

I. The chromosome movement during meiosis was worked out by 1900.

II. The chromosome movement during meiosis was worked out by 1902.

III. Walter Sutton and Theodore Boveri published their synthesis in 1902.

IV. The synthesis occurred immediately in 1865 after Mendel's publication.
Choose the correct option:
(1)I and III
(2)II and IV
(3)All of the above
(4)II and III
93.Assertion (A): In Morgan's Drosophila crosses, when the F1 hybrid female was crossed,
the F2 generation deviated significantly from the expected Mendelian 9:3:3:1 phenotypic ratio.

Reason (R): The genes for body colour and eye colour in Drosophila are located on the X
chromosome and show linkage, meaning they do not assort completely independently.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
94.T.H. Morgan studied X-linked genes in Drosophila. Which of the following represents the
CORRECT pairing of characters and mutant recessive phenotypes studied by him?

I. Body colour: Recessive mutant is Yellow, Dominant wild-type is Brown.

II. Eye colour: Recessive mutant is White, Dominant wild-type is Red.

III. Wing size: Recessive mutant is Miniature, Dominant wild-type is Normal.

IV. Eye colour: Recessive mutant is Red, Dominant wild-type is White.
Choose the correct option:
(1)I and II only
(2)I, II, and III
(3)All of the above
(4)II and IV
95.Assertion (A): Linkage completely restricts the independent assortment of genes and is
regarded as a major exception to Mendel's Law of Independent Assortment.

Reason (R): Mendel never encountered linkage because all seven characters he studied were
located on entirely different, non-homologous chromosomes.
(1)Option 2
(2)Option 4
(3)Option 3
(4)Option 1
96.In NCERT Figure 4.11 representing linkage experiments, which of the following
represents the CORRECT proportions of parentals and recombinants in Cross A and Cross B?

I. Cross A: Parental types = 98.7%, Recombinant types = 1.3%.

II. Cross B: Parental types = 62.8%, Recombinant types = 37.2%.

III. Cross A: Parental types = 62.8%, Recombinant types = 37.2%.

IV. Cross B: Parental types = 98.7%, Recombinant types = 1.3%.
Choose the correct option:
(1)I and IV
(2)II and IV
(3)I and II
(4)II and III
97.Assertion (A): Alfred Sturtevant deciphered that the recombination frequency between
gene pairs on the same chromosome could be used as a measure of the physical distance between
genes.

Reason (R): Sturtevant was a brilliant organic chemist who synthesized artificial nucleotide
linkages to physically cross-link Drosophila genes.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
98.Regarding the genetic notation used in Morgan's Drosophila crosses (Figure 4.11), which
of the following is/are CORRECT according to NCERT?

I. The wild-type alleles are represented with a plus (+) sign as superscript (e.g., y^+ and w^+).

II. The mutant alleles are represented in lowercase without any plus sign (e.g., y and w).

III. The Y chromosome carries dominant wild-type alleles for all X-linked genes studied.

IV. The presence of a plus (+) sign denotes that the allele is recessive to the mutant state.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)I and II
(4)II and IV
99.Assertion (A): The number of linkage groups in a diploid organism is exactly equal to its
haploid chromosome number.

Reason (R): Genes situated on the same chromosome belong to the same linkage group and
assort together unless separated by crossing over.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
100.Regarding cytological observations of chromosomes during cell division, which of the
following is/are CORRECT according to NCERT?

I. Chromosomes double and divide just before each cell division.

II. Chromosomes appear as stained 'colored bodies' in the nucleus when viewed under
microscopes.

III. The behavior of chromosomes during mitosis is completely different from their behavior
during meiosis.

IV. The movement of chromosomes was fully worked out cytologically by the year 1865.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)I and II
(4)II and IV
101.Assertion (A): Walter Sutton used the physical movement of chromosomes during meiosis
to explain and justify Gregor Mendel's laws of inheritance.

Reason (R): Sutton argued that the pairing and segregation of homologous chromosome pairs
lead directly to the independent segregation of the alleles they carry.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
102.Mendel's concept of genes (factors) as stable, discrete units was rejected by his
contemporaries for which of the following reasons in NCERT?

I. Contemporary biologists believed in continuous variation as the major pattern in nature.

II. Mendel's discrete factors did not show any blending or intermediate states, which clashed
with the idea of continuous variation.

III. Biologists believed that genes were highly unstable and mutated constantly.

IV. Mendel's factors were proved to be made of highly volatile proteins.
Choose the correct option:
(1)II and IV
(2)I, II, and III
(3)I and II
(4)All of the above
103.Assertion (A): Gregor Mendel was unable to provide physical proof for the existence of
factors or show what they were biochemically made of.

Reason (R): The chemical structure of DNA and the presence of chromosomes in the nucleus
were completely discovered and accepted in 1865.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
104.In T.H. Morgan's Drosophila crosses, which of the following represents the CORRECT
genetic genotypes of the parental flies in Cross A (yellow-white)?

I. Female parent genotype: y w / y w.

II. Male parent genotype: y^+ w^+ / Y.

III. Female parent genotype: y^+ w^+ / y^+ w^+.

IV. Male parent genotype: y w / Y.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)II and IV
(4)I and II
105.Assertion (A): Morgan and his group carried out dihybrid crosses in Drosophila where
the genes were located specifically on the X chromosome.

Reason (R): Sex-linked recessive traits are always expressed exclusively in female fruit flies
because they carry two copies of the X chromosome.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
106.In linkage studies, what is the maximum theoretical frequency of recombination between
any two genes on a chromosome under normal meiotic conditions according to NCERT
principles?

I. The maximum recombination frequency is exactly 50%.

II. The maximum recombination frequency is exactly 100%.

III. If recombination is 50%, the genes show independent assortment and behave as if they are
on separate chromosomes.

IV. If recombination is 0%, the genes exhibit complete, absolute linkage.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV
(4)I, III, and IV
107.Assertion (A): Recombination is physically caused by the crossing over between non-sister
chromatids of homologous chromosomes during meiosis.

Reason (R): Crossing over occurs during the pachytene stage of Prophase I, leading to the
exchange of genetic segments between maternal and paternal chromosomes.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
108.Morgan's Cross B studied white eye and miniature wing genes. Which of the following
descriptions represents the CORRECT phenotypes of the parental flies in this cross according to
NCERT Figure 4.11?

I. Female parent: white-eyed and miniature-winged (w m / w m).

II. Male parent: red-eyed and normal-winged (wild-type, w^+ m^+ / Y).

III. Female parent: red-eyed and normal-winged (w^+ m^+ / w^+ m^+).

IV. Male parent: white-eyed and miniature-winged (w m / Y).
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV
(4)I and II
109.Assertion (A): If the recombination frequency between two genes on a chromosome is
1.3%, their mapped distance is exactly 1.3 map units.

Reason (R): Sturtevant defined one map unit (or centimorgan) as equivalent to a 10%
recombination frequency between two genes.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
110.In Morgan's Cross B (white eye and miniature wing), which of the following represents
the CORRECT list of recombinant offspring phenotypes recovered in the F2 generation
according to NCERT Figure 4.11?

I. White-eyed, normal-winged flies.

II. Red-eyed, miniature-winged flies.

III. Red-eyed, normal-winged flies.

IV. White-eyed, miniature-winged flies.
Choose the correct option:
(1)I, II, and III
(2)I and II
(3)II and IV
(4)All of the above
111.Assertion (A): Human skin colour is a classic example of polygenic inheritance controlled
by three genes: A, B, and C.

Reason (R): In this system, the phenotype is determined by the total number of dominant alleles,
giving a continuous gradient of skin tones rather than distinct categories.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
112.Which of the following statements represents the CORRECT properties of polygenic
inheritance according to NCERT?

I. Polygenic inheritance typically controls traits that are spread across a gradient, such as
human height or skin colour.

II. Polygenic traits are controlled by a single gene with multiple alleles present in a diploid cell.

III. Polygenic inheritance takes into account the significant influence of the environment on
phenotype expression.

IV. The phenotypic expression of polygenic traits is strictly discrete, showing no intermediate
states.
Choose the correct option:
(1)I, II, and III
(2)I and III
(3)II and IV
(4)All of the above
113.Assertion (A): Pleiotropy is a genetic phenomenon where a single gene exhibits multiple
phenotypic expressions within an organism.

Reason (R): A pleiotropic gene is always controlled by multiple alleles located on different non-
homologous chromosomes in a population.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
114.Regarding the disease Phenylketonuria (PKU) as a classic example of pleiotropy, which of
the following phenotypic symptoms are manifested by a single gene mutation according to
NCERT?

I. Mental retardation.

II. Reduction in hair and skin pigmentation.

III. Formation of highly pigmented skin lesions and tumors.

IV. Severe respiratory distress and cystic fibrosis.
Choose the correct option:
(1)I, II, and III
(2)II and IV
(3)All of the above
(4)I and II
115.Assertion (A): The gene B controlling starch synthesis in pea seeds exhibits incomplete
dominance when we examine starch grain size as the phenotype.

Reason (R): Heterozygous Bb seeds produce starch grains of intermediate size, unlike the large
grains of BB and small grains of bb.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
116.Regarding the starch synthesis gene B in pea seeds, which of the following pairings of
genotypes and phenotypic outcomes is/are CORRECT according to NCERT?

I. BB: Large starch grains and round seeds.

II. bb: Small starch grains and wrinkled seeds.

III. Bb: Intermediate starch grains and wrinkled seeds.

IV. Bb: Intermediate starch grains and round seeds.
Choose the correct option:
(1)II, III, and IV
(2)I and II only
(3)All of the above
(4)I, II, and IV
117.Assertion (A): Henking (1891) traced a specific nuclear structure through
spermatogenesis in half of the sperm of certain insects and called it the 'X body'.

Reason (R): Henking recognized that the X body was the female-determining chromosome, and
successfully observed its pairing with autosomes under electron microscopes.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
118.Regarding the XO sex determination mechanism in insects like the grasshopper, which of
the following statements is/are CORRECT according to NCERT?

I. All eggs bear an additional X chromosome in addition to the autosomes.

II. Sperms are of two types: 50% carry an X chromosome, and 50% have no X chromosome
(denoted as O).

III. Fertilization of an egg with an X-bearing sperm yields a male offspring.

IV. The grasshopper is an example of male heterogamety.
Choose the correct option:
(1)I, II, and IV
(2)All of the above
(3)I, II, and III
(4)II and IV only
119.Assertion (A): Humans and Drosophila both exhibit the XY type of sex determination,
which is classified as male heterogamety.

Reason (R): In both species, the females produce only one type of gamete (eggs carrying an X
chromosome), whereas males produce two types of gametes (sperms carrying either X or Y).
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
120.Regarding the sex determination mechanism in birds, which of the following statements
is/are CORRECT according to NCERT?

I. Birds exhibit female heterogamety, where females produce two different types of gametes.

II. The sex chromosomes in birds are designated as Z and W.

III. Female birds possess the homozygous sex chromosome genotype ZZ, while males have ZW.

IV. The sex of the offspring in birds is determined entirely by the genetic contribution of the egg
(female parent).
Choose the correct option:
(1)I, II, and III
(2)II and IV only
(3)I, II, and IV
(4)All of the above
121.Assertion (A): In birds, the sex of the chick is determined entirely by the sperm of the
father during fertilization.

Reason (R): Male birds are homogametic (ZZ) and produce only one type of sperm carrying the
Z chromosome, whereas female birds are heterogametic (ZW) and produce two types of eggs.
(1)Option 2
(2)Option 1
(3)Option 4
(4)Option 3
122.Which of the following pairings of organisms and their sex-determination mechanisms
is/are CORRECT according to NCERT?

I. Grasshopper: XO type (male heterogamety).

II. Drosophila: XY type (male heterogamety).

III. Birds: ZW type (female heterogamety).

IV. Humans: XY type (female heterogamety).
Choose the correct option:
(1)II, III, and IV
(2)All of the above
(3)I and II only
(4)I, II, and III
123.Assertion (A): In both humans and Drosophila, the males carry an XY chromosome pair,
while the females carry an XX chromosome pair.

Reason (R): The total chromosome number in a diploid human cell is 46, and in a diploid
Drosophila cell is 8.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
124.In the polygenic skin colour system controlled by three genes (A, B, C), which of the
following represents the CORRECT dosage phenotypes according to NCERT?

I. The genotype AABBCC has 6 dominant alleles and expresses the darkest skin colour.

II. The genotype aabbcc has 0 dominant alleles and expresses the lightest skin colour.

III. Genotypes with exactly 3 dominant alleles (e.g., AaBbCc) express an intermediate skin
colour.

IV. The genotype Aabbcc has 1 dominant allele and behaves as completely dominant dark skin
colour.
Choose the correct option:
(1)All of the above
(2)I and II only
(3)I, II, and III
(4)II and IV
125.Assertion (A): In polygenic inheritance, the phenotypic expression of a trait is determined
by the cumulative, additive effect of each allele present.

Reason (R): Each dominant allele contributes a distinct, discrete dosage to the phenotype,
meaning dominance is completely co-expressed at the molecular level.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
126.Regarding the biological basis of the pleiotropic disease Phenylketonuria (PKU), which of
the following is/are CORRECT according to NCERT?

I. The disease is caused by a mutation in a single gene that codes for the enzyme phenylalanine
hydroxylase.

II. The disease is caused by the lack of the enzyme tyrosine hydroxylase, leading to tyrosine
accumulation.

III. The affected enzyme normally catalyzes the conversion of the amino acid phenylalanine into
tyrosine.

IV. The clinical symptoms are a direct result of a single metabolic block yielding widespread
systemic outcomes.
Choose the correct option:
(1)I, III, and IV
(2)All of the above
(3)II, III, and IV
(4)I and II only
127.Assertion (A): If we examine seed shape as the phenotype in pea plants, the allele B is
completely dominant over the allele b in the heterozygote Bb.

Reason (R): Heterozygous Bb seeds are round in shape, which is phenotypically
indistinguishable from the homozygous dominant BB parent.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
128.The gene B controlling starch synthesis in pea seeds exhibits different dominance states
depending on the chosen phenotype. Which of the following is/are CORRECT according to
NCERT?

I. For seed shape, the alleles show complete dominance.

II. For starch grain size, the alleles show incomplete dominance.

III. For seed shape, the alleles show incomplete dominance.

IV. For starch grain size, the alleles show co-dominance.
Choose the correct option:
(1)All of the above
(2)I and II
(3)I, II, and III
(4)II and IV
129.Assertion (A): In Henking's experiments, the 'X body' was received by exactly 50 percent
of the sperm cells during spermatogenesis.

Reason (R): The 'X body' is a haploid autosome that undergoes regular mitotic replication in
somatic cells, ensuring equal distribution to all sperm cells.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
130.Regarding the division of chromosomes in a cell, which of the following descriptions is/are
CORRECT according to NCERT?

I. Chromosomes involved in sex determination are called sex chromosomes.

II. All chromosomes other than sex chromosomes are called autosomes.

III. The total number of autosomes is always equal to the total number of sex chromosomes in
all organisms.

IV. In all organisms, the presence of autosomes is not required for sex determination.
Choose the correct option:
(1)II and IV
(2)I and II
(3)All of the above
(4)I, II, and III
131.Assertion (A): In grasshoppers, the male parent produces exactly two types of sperms,
whereas the female parent produces only one type of egg.

Reason (R): Grasshopper males are heterogametic (XO) producing 50% X-bearing sperms and
50% O-bearing (lacking X) sperms, while females are homogametic (XX).
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
132.Regarding human sex chromosomes as described in NCERT, which of the following
statements is/are CORRECT?

I. Human females carry a pair of X chromosomes (XX) in addition to 22 pairs of autosomes.

II. Human males carry one X and one Y chromosome (XY) in addition to 22 pairs of autosomes.

III. The Y chromosome in males is identical in size and shape to the X chromosome.

IV. Human males carry a pair of Y chromosomes (YY) in addition to autosomes.
Choose the correct option:
(1)II and IV
(2)All of the above
(3)I and II
(4)I, II, and III
133.Assertion (A): In Drosophila, sex determination follows the XY mechanism, making males
heterogametic and females homogametic.

Reason (R): Fruit fly males produce two types of eggs carrying either the Z or W chromosome,
whereas females produce only one type of sperm.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
134.Which of the following descriptions is/are CORRECT regarding sex chromosomes and
gametes in birds according to NCERT?

I. Male birds are homogametic and possess the sex chromosomes ZZ.

II. Female birds are heterogametic and possess the sex chromosomes ZW.

III. Male birds produce two distinct types of sperms in equal proportions.

IV. Female birds produce two distinct types of eggs in equal proportions.
Choose the correct option:
(1)I, II, and IV
(2)All of the above
(3)II and IV only
(4)I, II, and III
135.Assertion (A): In birds, the sex of the progeny is determined entirely by the genetic
composition of the female gamete (egg) that is fertilized.

Reason (R): The female bird produces two types of eggs (50% carrying Z, 50% carrying W)
which unite with a single type of Z-bearing sperm from the homogametic male.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
136.In grasshoppers, which of the following is/are the CORRECT count of sex chromosomes
present in somatic cells of males and females according to NCERT?

I. Somatic cells of females contain exactly two X chromosomes (XX).

II. Somatic cells of males contain only a single X chromosome (XO).

III. Males have one less chromosome in total than females.

IV. Males have one extra chromosome in total than females.
Choose the correct option:
(1)II and III only
(2)I, II, and IV
(3)I, II, and III
(4)I and IV only
137.Assertion (A): To avoid confusion with the human XY system, the sex chromosomes of
birds are designated as Z and W chromosomes.

Reason (R): In birds, the female has Z and W chromosomes (ZW), while the male has two Z
chromosomes (ZZ).
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
138.Starch synthesis in pea seeds is controlled by gene B. Which of the following statements
represents the CORRECT starch grain size and seed shape details according to NCERT?

I. Homozygous BB seeds have large starch grains and are round in shape.

II. Homozygous bb seeds have small starch grains and are wrinkled in shape.

III. Heterozygous Bb seeds have intermediate-sized starch grains and are round in shape.

IV. Heterozygous Bb seeds have intermediate-sized starch grains and are wrinkled in shape.
Choose the correct option:
(1)II and IV
(2)I, II, and III
(3)All of the above
(4)I and II only
139.Assertion (A): Dominance is not an autonomous feature of a gene, and the allele B
behaves as dominant or incomplete dominant depending on the phenotype we choose to
examine.

Reason (R): The Bb heterozygote produces round seeds showing complete dominance for seed
shape, but produces intermediate-sized starch grains showing incomplete dominance for grain
size.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
140.Polygenic inheritance in a population typically yields which of the following phenotype
distributions according to NCERT principles?

I. A continuous gradient of phenotypes spread across a spectrum.

II. A bell-shaped normal distribution curve showing very few extremes and a high proportion of
intermediates.

III. Only two highly distinct parental phenotypes with no intermediate states.

IV. Equal proportions of all genotypes and phenotypes in a 1:1:1:1 ratio.
Choose the correct option:
(1)II and IV
(2)All of the above
(3)I, II, and III
(4)I and II
141.Assertion (A): Male honeybees (drones) are haploid carrying exactly 16 chromosomes,
while female honeybees (queens and workers) are diploid carrying exactly 32 chromosomes.

Reason (R): Drones develop parthenogenetically from unfertilized eggs produced by the queen,
whereas females develop from fertilized eggs.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
142.Regarding the haplodiploid lineage of honeybees, which of the following genetic
statements is/are CORRECT according to NCERT?

I. Drones (males) have no father and cannot have sons.

II. Drones (males) have a grandfather and can have grandsons.

III. Male honeybees produce sperms by the process of meiosis.

IV. Female honeybees (queens) produce eggs by the process of mitosis.
Choose the correct option:
(1)I and II
(2)All of the above
(3)II and IV only
(4)I, II, and III
143.Assertion (A): A male honeybee (drone) cannot have a son, but can theoretically have a
grandson.

Reason (R): A drone develops from an unfertilized egg carrying only the mother's maternal
genes, but can fertilize a female queen's egg to produce a diploid female daughter who can
subsequently lay unfertilized male eggs.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
144.Regarding the genetics of mutations as described in NCERT, which of the following
statements is/are CORRECT?

I. Mutation is a phenomenon which results in alteration of DNA sequences.

II. Mutations lead to changes in the genotype and the phenotype of an organism.

III. Loss (deletion) or gain (insertion/duplication) of a segment of DNA results in alterations in
chromosomes.

IV. Alterations in chromosomes are commonly observed in normal, healthy somatic cells.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)I and II only
(4)II and IV
145.Assertion (A): A classical example of a point mutation is a change of a single base pair in
the gene for beta-globin chain that results in sickle-cell anaemia.

Reason (R): Deletion and insertion of base pairs of DNA cause frame-shift mutations, which
completely alter the reading frame of all codons from the point of mutation onwards.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)(A) is true but (R) is false.
146.Regarding the agents that induce mutations as described in NCERT, which of the
following statements is/are CORRECT?

I. Chemical and physical factors that induce mutations are called mutagens.

II. UV radiation is a classical example of a physical mutagen.

III. UV radiation is a highly ionizing radiation that induces mutations only in plant cells.

IV. Water is the primary chemical mutagen in all living organisms.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV
(4)I and II
147.Assertion (A): In human genetics, pedigree analysis is used as a powerful tool to study the
inheritance of a particular trait over several generations.

Reason (R): Controlled hybridization crosses, like those performed by Mendel in garden peas,
are highly ethical and easily performed in human populations.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
148.Regarding the pedigree chart symbols represented in NCERT Figure 4.13, which of the
following pairings of symbols and definitions is/are CORRECT?

I. Square represents Male, Circle represents Female.

II. Diamond represents Sex Unspecified.

III. Shaded symbols represent Unaffected individuals, while open symbols represent Affected
individuals.

IV. A horizontal line connecting a male and female symbol represents Mating.
Choose the correct option:
(1)I, II, and IV
(2)II and IV only
(3)I, II, and III
(4)All of the above
149.Assertion (A): In a pedigree chart, a double horizontal line connecting a male and a
female symbol represents mating between relatives (consanguineous mating).

Reason (R): Consanguineous matings significantly increase the frequency of homozygous
dominant lethal disorders in a family line.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
150.NCERT Figure 4.14 represents two pedigree charts: Chart (a) and Chart (b). Which of
the following descriptions matches the CORRECT genetic inheritance patterns of these charts?

I. Chart (a) represents an Autosomal Dominant trait, such as Myotonic Dystrophy.

II. Chart (b) represents an Autosomal Recessive trait, such as Sickle-cell anaemia.

III. Chart (a) represents a Sex-linked Recessive trait, such as Haemophilia.

IV. Chart (b) represents a Sex-linked Dominant trait, such as Vitamin D resistant rickets.
Choose the correct option:
(1)I and II
(2)II and IV
(3)All of the above
(4)I, II, and III
151.Assertion (A): In an autosomal dominant pedigree (such as Myotonic Dystrophy), the
affected trait never skips a generation, and every affected child must have at least one affected
parent.

Reason (R): A dominant allele is expressed in both the homozygous and heterozygous states,
meaning the trait cannot remain hidden in carrier parents.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
152.In honeybees, which of the following is/are the CORRECT genetic count of chromosomes
present in the somatic cells of the queen, worker, and drone honeybees respectively?

I. Queen honeybee: 32 chromosomes (diploid).

II. Worker honeybee: 32 chromosomes (diploid).

III. Drone honeybee: 16 chromosomes (haploid).

IV. Drone honeybee: 8 chromosomes (haploid).
Choose the correct option:
(1)II and III only
(2)I, II, and III
(3)All of the above
(4)I, II, and IV
153.Assertion (A): A male honeybee (drone) produces haploid sperms through the process of
mitosis instead of meiosis.

Reason (R): Drones develop parthenogenetically from haploid eggs and are already haploid,
meaning meiotic division would reduce their genome further to an unviable state.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
154.Which of the following descriptions regarding pedigree analysis is/are CORRECT
according to NCERT?

I. The pedigree study provides a strong record of family history about the inheritance of a
particular trait.

II. In a pedigree chart, the inheritance of a specific trait is represented as a tree over several
generations.

III. Pedigree analysis is utilized extensively to diagnose chromosomal aneuploidy in newborn
infants.

IV. Pedigree charts are constructed by genetically crossing human parents in laboratories.
Choose the correct option:
(1)All of the above
(2)II and IV
(3)I and II
(4)I, II, and III
155.Assertion (A): In an autosomal recessive pedigree (such as Sickle-cell anaemia), two
completely unaffected parents can have an affected child.

Reason (R): Unaffected parents can be heterozygous carriers (carrying one copy of the recessive
disease allele) and pass it on, allowing the trait to skip generations and appear suddenly in
homozygous offspring.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
156.In NCERT Figure 4.13, which of the following represents the CORRECT pairing of
pedigree diagrams and mating status?

I. A single horizontal line connecting male and female = Mating.

II. A double horizontal line connecting male and female = Mating between relatives
(consanguineous mating).

III. A single vertical line extending downwards from mating line = Offspring.

IV. A circle with a diagonal slash = Sterile female.
Choose the correct option:
(1)All of the above
(2)I, II, and III
(3)I and II only
(4)II, III, and IV
157.Assertion (A): In a pedigree chart, a diamond-shaped symbol is used to represent an
individual whose sex is unspecified.

Reason (R): The diamond symbol is shaded when the unspecified individual is affected by the
genetic disorder.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
158.According to NCERT, alterations in chromosomes are commonly observed in which of the
following cell types?

I. Normal diploid zygotes.

II. Cancer cells.

III. Haploid drone honeybee cells.

IV. Active somatic cells during mitotic telophase.
Choose the correct option:
(1)II and IV
(2)II only
(3)II and III
(4)I and II
159.Assertion (A): Insertion or deletion of one or two base pairs in a coding DNA segment
causes a frameshift mutation, completely altering the downstream polypeptide sequence.

Reason (R): Triplet codons are read continuously without punctuations, meaning any change in
base number shifts the entire reading frame from that point onwards.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
160.Regarding the disease Myotonic Dystrophy represented in NCERT Figure 4.14(a), which
of the following genetic descriptions is/are CORRECT?

I. The disease is an autosomal dominant disorder.

II. The disease is an autosomal recessive disorder.

III. Unaffected parents in the pedigree chart can have affected children.

IV. Affected parents can pass the trait to both male and female children equally.
Choose the correct option:
(1)I and IV
(2)I and III only
(3)All of the above
(4)II and IV
161.Assertion (A): A male drone honeybee has 16 chromosomes and produces haploid sperms
that also carry exactly 16 chromosomes.

Reason (R): Spermatogenesis in drones involves mitotic division, which maintains the identical
chromosome number of the parent cell in the resulting sperm gametes.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
162.In NCERT Figure 4.13, a symbol consisting of an open diamond with a number '5′
written inside denotes which of the following descriptions?

I. Five affected male offspring.

II. Five unaffected offspring of unspecified sex.

III. Five carrier female offspring.

IV. Five consanguineous matings in the family line.
Choose the correct option:
(1)I and II
(2)II and IV
(3)II and III
(4)II only
163.Assertion (A): In the autosomal recessive pedigree in Figure 4.14(b), the parents in the
first generation are completely unaffected but carry the disease allele.

Reason (R): Autosomal recessive traits can remain hidden in heterozygous carriers and are
expressed only when both parents pass on the recessive allele to a homozygous offspring.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
164.In honeybees, which of the following social castes are produced from fertilized eggs and
are therefore genetically diploid?

I. Queen honeybees.

II. Worker honeybees.

III. Drone honeybees.

IV. Soldier honeybees.
Choose the correct option:
(1)All of the above
(2)I and II
(3)II and IV
(4)I, II, and III
165.Assertion (A): Sickle-cell anaemia in human families is tracked using autosomal recessive
pedigree patterns as shown in Figure 4.14(b).

Reason (R): The disease is caused by a dominant mutant allele located on the sex-determining Y
chromosome of human males.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
166.Which of the following is/are the molecular event(s) involved in mutations according to
NCERT?

I. Alteration of DNA sequences.

II. Deletion of DNA segments.

III. Insertion or duplication of DNA segments.

IV. Complete conversion of DNA into RNA in somatic cells.
Choose the correct option:
(1)II and IV
(2)I and II only
(3)All of the above
(4)I, II, and III
167.Assertion (A): Pedigree analysis is the primary method used to trace the inheritance of
specific abnormality traits in human families.

Reason (R): In human populations, controlled laboratory hybridization crosses cannot be
performed due to ethical boundaries and biological constraints.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
168.In a pedigree showing an autosomal dominant trait (such as Myotonic Dystrophy), which
of the following offspring-parent scenarios is/are CORRECT according to NCERT?

I. An affected child must have at least one affected parent.

II. Two completely unaffected parents can have an affected child.

III. Unaffected parents can never pass on the dominant trait to their offspring.

IV. Affected parents can have completely unaffected children if they are heterozygous.
Choose the correct option:
(1)All of the above
(2)I and II
(3)I, III, and IV
(4)II and IV
169.Assertion (A): In an autosomal dominant pedigree, the disease phenotype is expressed in
both the homozygous and heterozygous genotypes.

Reason (R): Heterozygous individuals (Aa) show a much milder form of the disease than
homozygous dominant individuals (AA), allowing them to be classified as carriers.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
170.Which of the following processes is/are involved in the parthenogenetic development of
drone honeybees according to NCERT?

I. The queen honeybee undergoes meiosis to produce haploid eggs carrying 16 chromosomes.

II. The haploid eggs develop directly into male drones without undergoing fertilization.

III. The eggs are fertilized by mitotic sperms from the drone, and then lose their paternal
chromosomes to become haploid drones.

IV. Drones develop from diploid zygotes that actively shed half of their chromosomes.
Choose the correct option:
(1)I and II
(2)All of the above
(3)I, II, and III
(4)II and IV
171.Assertion (A): Recombination and mutation are the only two cytological phenomena that
lead to variation in DNA sequence and structure.

Reason (R): While recombination reshuffles existing alleles during meiotic crossing over,
mutation is the primary phenomenon that results in direct alteration of DNA sequences
themselves.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
172.Which of the following statements regarding chromosomal alterations is/are CORRECT
according to NCERT?

I. A single DNA helix runs continuously from one end to the other in each chromatid in a highly
supercoiled form.

II. Loss (deletions) or gain (insertion/duplication) of a segment of DNA results in alterations in
chromosomes.

III. Alterations in chromosomes are commonly observed in normal, healthy somatic cells to
facilitate division.

IV. Chromosomal aberrations is the technical term for these abnormalities, which are commonly
observed in cancer cells.
Choose the correct option:
(1)All of the above
(2)II and IV only
(3)I, II, and III
(4)I, II, and IV
173.Assertion (A): Sickle cell anemia is considered a classical example of a point mutation.

Reason (R): Point mutations are defined by a change in a single base pair of DNA, which is the
exact molecular defect in the gene coding for the beta globin chain in sickle cell anemia.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
174.Regarding the agents that induce mutations as described in NCERT, which of the
following statements is/are CORRECT?

I. Many chemical and physical factors that induce mutations are referred to as mutagens.

II. UV radiations can cause mutations in organisms and are classified as mutagens.

III. UV radiation is a classical example of a chemical mutagen.

IV. Mutation mechanisms are fully detailed in the current NCERT level 12th text.
Choose the correct option:
(1)I, II, and III
(2)I and II
(3)All of the above
(4)II and IV only
175.Assertion (A): In human genetics, pedigree analysis is used as a strong alternative tool to
study the inheritance of a particular trait over generations.

Reason (R): Controlled crosses that can be performed in pea plants are not possible in human
beings due to ethical and biological constraints.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
176.Regarding the standard pedigree symbols represented in NCERT Figure 4.13, which of
the following statements is/are CORRECT?

I. A square symbol represents a Male.

II. A circle symbol represents a Female.

III. A diamond symbol represents Sex Unspecified.

IV. A hexagon symbol represents a Hermaphrodite.
Choose the correct option:
(1)I, II, and III
(2)I and II only
(3)All of the above
(4)II, III, and IV
177.Assertion (A): In a pedigree chart, shaded square, circle, or diamond symbols always
represent affected individuals.

Reason (R): A single horizontal line between a male and a female symbol represents a sibling
relationship between them.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)(A) is true but (R) is false.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
178.Regarding the complex pedigree symbols in NCERT Figure 4.13, which of the following
pairings of diagrams and meanings is/are CORRECT?

I. A double horizontal line between male and female represents mating between relatives
(consanguineous mating).

II. Parents are shown above and children below in order of birth from left to right.

III. Parents with a shaded male child is represented by a vertical line leading to a shaded
square.

IV. A diamond with a number '5′ inside represents 'five unaffected offspring'.
Choose the correct option:
(1)II and IV only
(2)All of the above
(3)I and IV only
(4)I, II, and III only
179.Assertion (A): Mendelian disorders are mainly determined by alteration or mutation in a
single gene.

Reason (R): These disorders are transmitted to the offspring on the same lines as described in
the Mendelian principles of inheritance, and can be traced in a family by pedigree analysis.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
180.According to NCERT, which of the following are classified as common and prevalent
Mendelian disorders in human beings?

I. Haemophilia and Cystic fibrosis

II. Sickle-cell anaemia and Colour blindness

III. Phenylketonuria and Thalassemia

IV. Down's syndrome and Turner's syndrome
Choose the correct option:
(1)II, III, and IV
(2)I, II, and III
(3)I and II only
(4)All of the above
181.Assertion (A): By pedigree analysis, one can easily understand whether the Mendelian
trait in question is dominant or recessive.

Reason (R): Dominant autosomal traits (like myotonic dystrophy) can easily skip generations,
appearing suddenly in the offspring of completely unaffected parents.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
182.Regarding the representative pedigree charts shown in NCERT Figure 4.14, which of the
following statements is/are CORRECT?

I. Pedigree chart (a) represents an autosomal dominant trait, for which myotonic dystrophy is
the representative example.

II. Pedigree chart (b) represents an autosomal recessive trait, for which sickle-cell anaemia is
the representative example.

III. In pedigree chart (a), completely unaffected parents are shown having affected children.

IV. In pedigree chart (b), affected parent couples are shown having only unaffected children.
Choose the correct option:
(1)II and IV only
(2)All of the above
(3)I and II
(4)I, II, and III
183.Assertion (A): Colour blindness is a sex-linked recessive disorder that results in the
failure to discriminate between red and green colours.

Reason (R): This defect is due to mutation in certain genes present in the Y chromosome that
code for the red and green cone cells of the eye.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
184.Regarding the frequency and genetic basis of colour blindness as described in NCERT,
which of the following statements is/are CORRECT?

I. It occurs in about 8 per cent of males.

II. It occurs in only about 0.4 per cent of females.

III. Females have a much lower occurrence because they have two X chromosomes, requiring
two copies of the mutant gene to express it.

IV. Males have only one X chromosome, meaning a single copy of the mutant gene leads to
expression.
Choose the correct option:
(1)II and IV only
(2)I and IV only
(3)All of the above
(4)I, II, and III only
185.Assertion (A): The son of a carrier woman (heterozygous for colour blindness) has exactly
a 50 per cent chance of being colour blind.

Reason (R): The mother herself is not colour blind because the mutant gene is recessive, and its
effect is suppressed by her matching dominant normal gene.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
186.Regarding the requirements for a female daughter to be phenotypically colour blind,
which of the following is/are CORRECT according to NCERT?

I. The daughter will not normally be colour blind unless her mother is at least a carrier.

II. The daughter's father must be colour blind.

III. The daughter can be colour blind if her father is normal but mother is homozygous colour
blind.

IV. The daughter will always be colour blind if her mother is a carrier and father is normal.
Choose the correct option:
(1)I and II
(2)I, II, and III
(3)All of the above
(4)II and IV only
187.Assertion (A): Haemophilia is a sex-linked recessive disease that shows transmission from
an unaffected carrier female to some of her male progeny.

Reason (R): Heterozygous carrier females are unaffected because they carry a matching
dominant normal clotting gene, but can pass their single mutant X chromosome to 50 per cent of
their sons who lack a second X chromosome to suppress it.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
188.Regarding the molecular defect in haemophilia as described in NCERT, which of the
following statements is/are CORRECT?

I. A single protein that is a part of the cascade of proteins involved in the clotting of blood is
affected.

II. Due to this single protein defect, a simple cut in an affected individual results in non-stop
bleeding.

III. The disease is caused by the complete absence of red blood cells in the circulating blood.

IV. Multiple protein chains are simultaneously mutated, preventing oxygen binding.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV only
(4)I and II
189.Assertion (A): The possibility of a human female becoming homozygous haemophilic is
extremely rare.

Reason (R): For a female to be affected, her mother has to be at least a carrier and her father
must be haemophilic, a paternal genotype that is generally unviable in the later stage of life.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
190.Regarding the historical pedigree of the British Royal Family as described in NCERT,
which of the following statements is/are CORRECT?

I. The family pedigree of Queen Victoria shows a number of haemophilic descendants.

II. Queen Victoria was herself a carrier of the haemophilia disease.

III. Queen Victoria was homozygous haemophilic and suffered from severe bleeding.

IV. Queen Victoria inherited the disease from her haemophilic father who died in infancy.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)II and IV only
(4)I and II
191.Assertion (A): Sickle-cell anaemia is an autosome-linked recessive trait that can be
transmitted from parents to offspring only when both partners are carriers for the gene.

Reason (R): In autosomal recessive inheritance, an offspring requires two copies of the mutant
allele to be affected, which can only be inherited if both parent partners are at least
heterozygous carriers.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
192.Regarding the genetic control of sickle-cell anaemia as described in NCERT, which of the
following statements is/are CORRECT?

I. The disease is controlled by a single pair of alleles: HbA and HbS.

II. Homozygous individuals for HbS (HbSHbS) show the diseased phenotype.

III. Heterozygous (HbAHbS) individuals appear apparently unaffected but are carriers of the
disease.

IV. Homozygous HbA (HbAHbA) individuals are carriers that exhibit the sickle-cell trait.
Choose the correct option:
(1)I and II only
(2)II and IV only
(3)All of the above
(4)I, II, and III
193.Assertion (A): Heterozygous HbAHbS individuals exhibit the sickle-cell trait and are
unaffected carriers.

Reason (R): There is exactly a 50 per cent probability of transmission of the mutant gene from a
heterozygous carrier parent to any progeny.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
194.Regarding the biochemical defect in sickle-cell anaemia as described in NCERT, which of
the following is/are CORRECT?

I. The defect is caused by the substitution of Glutamic acid (Glu) by Valine (Val).

II. The substitution occurs at the sixth position of the beta globin chain of the haemoglobin
molecule.

III. The substitution occurs at the sixth position of the alpha globin chain of the haemoglobin
molecule.

IV. The substitution is caused by Glutamic acid replacing Valine at the first position.
Choose the correct option:
(1)II and IV only
(2)I and III
(3)All of the above
(4)I and II
195.Assertion (A): The primary genetic defect in sickle-cell anaemia is a single base
substitution in the beta globin gene.

Reason (R): This single base substitution alters the sixth codon of the beta globin gene from
GUG to GAG.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is false but (R) is true.
196.Regarding the physiological consequences of the mutant haemoglobin in sickle-cell
individuals, which of the following is/are CORRECT according to NCERT?

I. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension.

II. The polymerisation causes a change in the shape of the RBC from a biconcave disc to an
elongated, sickle-like structure.

III. The mutant haemoglobin undergoes polymerisation under high oxygen tension.

IV. The shape change is from a sickle-like structure to a normal biconcave disc.
Choose the correct option:
(1)All of the above
(2)I and II
(3)II and IV only
(4)I and III
197.Assertion (A): Phenylketonuria is an inborn error of metabolism inherited as an
autosome-linked recessive trait.

Reason (R): Affected individuals lack a functional enzyme that directly converts the amino acid
tyrosine into phenylalanine.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
198.When the enzyme converting phenylalanine to tyrosine is deficient in phenylketonuria,
which of the following biochemical events occur according to NCERT?

I. Phenylalanine is accumulated in the tissues.

II. Phenylalanine is converted into phenylpyruvic acid and other derivatives.

III. Tyrosine is accumulated and converted into phenylpyruvic acid.

IV. Phenylalanine is rapidly converted into tyrosine and excreted in sweat.
Choose the correct option:
(1)II and IV only
(2)I and II
(3)I and III
(4)All of the above
199.Assertion (A): In phenylketonuria, the accumulated phenylpyruvic acid and other
derivatives are excreted through urine.

Reason (R): These accumulated molecules are very poorly reabsorbed by the kidney tubules.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
200.Regarding the clinical symptoms of phenylketonuria as stated in NCERT, which of the
following phenotypic manifestations is/are CORRECT?

I. Mental retardation

II. Reduction in hair pigmentation

III. Reduction in skin pigmentation

IV. Enlarged liver and hyper-pigmentation of the skin
Choose the correct option:
(1)All of the above
(2)II and IV only
(3)I and II only
(4)I, II, and III
201.Assertion (A): Thalassemia is an autosome-linked recessive blood disease that can be
transmitted from parents to offspring only when both partners are unaffected heterozygous
carriers.

Reason (R): The primary defect in thalassemia is a mutation or deletion that results in a
reduced rate of synthesis of one of the globin chains (alpha and beta chains) that make up
haemoglobin.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
202.Regarding the physiological and classification traits of Thalassemia as described in
NCERT, which of the following statements is/are CORRECT?

I. The defect ultimately results in a reduced rate of synthesis of one of the globin chains (a and b
chains).

II. The rate reduction causes the formation of abnormal haemoglobin molecules resulting in
anaemia.

III. Thalassemia can be classified according to which chain of the haemoglobin molecule is
affected.

IV. In beta Thalassemia, the production of the alpha globin chain is affected.
Choose the correct option:
(1)II and IV only
(2)I, II, and III
(3)All of the above
(4)I and II only
203.Assertion (A): Alpha Thalassemia is controlled by two closely linked genes, HBA1 and
HBA2, located on chromosome 16 of each parent.

Reason (R): The disease manifests due to the mutation or deletion of one or more of the four
alleles of these genes, and the fewer genes affected, the less alpha globin molecules are produced.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
204.Regarding the genetic control of beta Thalassemia as described in NCERT, which of the
following statements is/are CORRECT?

I. It is controlled by a single gene called HBB.

II. The gene HBB is located on chromosome 11 of each parent.

III. The disorder occurs due to mutation of one or both of the two alleles of this gene.

IV. The gene HBB is located on chromosome 16, closely linked to HBA1.
Choose the correct option:
(1)All of the above
(2)II and IV only
(3)I, II, and III
(4)I and II only
205.Assertion (A): Thalassemia is classified as a quantitative genetic problem, whereas sickle-
cell anaemia is classified as a qualitative genetic problem.

Reason (R): Thalassemia involves a reduced rate of synthesis of normal globin molecules, while
sickle-cell anaemia involves the synthesis of an incorrectly functioning mutant globin.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
206.Regarding the fundamental definition and causes of chromosomal disorders as described
in NCERT, which of the following statements is/are CORRECT?

I. Chromosomal disorders are caused due to the absence of one or more chromosomes.

II. Chromosomal disorders are caused due to the excess of one or more chromosomes.

III. Chromosomal disorders are caused due to the abnormal arrangement of one or more
chromosomes.

IV. Chromosomal disorders are exclusively caused by point mutations in somatic cell histones.
Choose the correct option:
(1)I, II, and III
(2)All of the above
(3)I and II only
(4)II and IV only
207.Assertion (A): Aneuploidy represents the gain or loss of a chromosome or chromosomes in
an organism.

Reason (R): Aneuploidy is caused by the failure of segregation of chromatids during the cell
division cycle.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
208.Which of the following are examples of aneuploidy in humans as stated in NCERT?

I. Down's syndrome, which results in the gain of an extra copy of chromosome 21.

II. Turner's syndrome, which results due to the loss of an X chromosome in human females.

III. Klinefelter's syndrome, which results from the gain of an extra X chromosome in males.

IV. Polygenic skin color inheritance, which results from multi-chromosomal cross-over.
Choose the correct option:
(1)I and II only
(2)All of the above
(3)I, II, and III
(4)II and IV only
209.Assertion (A): Polyploidy represents an increase in a whole set of chromosomes in an
organism.

Reason (R): Polyploidy is caused by the failure of cytokinesis after the telophase stage of cell
division.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
210.According to NCERT, which of the following statements regarding polyploidy and human
karyotype is/are CORRECT?

I. The phenomenon of polyploidy is often seen in plants.

II. The total number of chromosomes in a normal human somatic cell is 46 (23 pairs).

III. Out of 46 chromosomes in humans, 22 pairs are autosomes and one pair are sex
chromosomes.

IV. Normal human males have a pair of homogametic sex chromosomes represented as YY.
Choose the correct option:
(1)I, II, and III
(2)I and II only
(3)II and IV only
(4)All of the above
211.Assertion (A): Trisomy is the presence of an additional copy of a chromosome, whereas
monosomy is the lack of one chromosome from any one pair.

Reason (R): These numerical chromosomal anomalies are classified as polyploidy because they
change the total set of chromosomes in human somatic tissues.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
212.Which of the following are listed as common examples of chromosomal disorders in the
NCERT textbook?

I. Down's syndrome

II. Turner's syndrome

III. Klinefelter's syndrome

IV. Phenylketonuria and Cystic fibrosis
Choose the correct option:
(1)All of the above
(2)II and IV only
(3)I and II only
(4)I, II, and III
213.Assertion (A): Down's syndrome is a chromosomal disorder caused by the presence of an
additional copy of chromosome number 21.

Reason (R): This genetic condition represents a monosomy of chromosome number 21, resulting
in a total count of 45 chromosomes in somatic tissues.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
214.Regarding the historical discovery of Down's syndrome, which of the following is/are
CORRECT according to NCERT?

I. The disorder was first described by Langdon Down.

II. The discovery and first description occurred in the year 1866.

III. The disorder was first described by Thomas Hunt Morgan in 1910.

IV. Gregor Mendel first mathematically predicted this trisomy in 1865.
Choose the correct option:
(1)II and IV only
(2)All of the above
(3)I, II, and III
(4)I and II
215.Assertion (A): Individuals affected by Down's syndrome typically exhibit a small round
head with a flat back of head.

Reason (R): Their tongue is big and wrinkled, and their mouth is kept permanently closed to
prevent drooling.
(1)(A) is true but (R) is false.
(2)(A) is false but (R) is true.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
216.Regarding the clinical symptoms of Down's syndrome, which of the following features
is/are CORRECT according to NCERT?

I. Palm is broad with a characteristic palm crease.

II. Physical, psychomotor, and mental development is retarded.

III. Fingers exhibit many 'loops' on their tips.

IV. Affected individuals are completely fertile and develop normal secondary sexual
characteristics.
Choose the correct option:
(1)I and II only
(2)All of the above
(3)II and IV only
(4)I, II, and III
217.Assertion (A): Klinefelter's syndrome is a chromosomal disorder resulting in a karyotype
of 47, XXY.

Reason (R): This genetic condition is caused by the presence of an additional copy of the Y
chromosome in human somatic tissues.
(1)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
218.Regarding the clinical symptoms of Klinefelter's syndrome, which of the following
features is/are CORRECT according to NCERT?

I. The affected individual has an overall masculine development.

II. Feminine development, such as the development of breasts (Gynecomastia), is also expressed.

III. Affected individuals are highly sterile.

IV. Affected individuals are short-statured with underdeveloped muscles.
Choose the correct option:
(1)I, II, and III
(2)I and II only
(3)All of the above
(4)II and IV only
219.Assertion (A): Turner's syndrome is a chromosomal disorder resulting in a karyotype of
45 with X0.

Reason (R): This genetic condition is caused by the complete absence of one of the autosomes in
human female somatic tissues.
(1)(A) is false but (R) is true.
(2)(A) is true but (R) is false.
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
220.Regarding the clinical symptoms of Turner's syndrome, which of the following features
is/are CORRECT according to NCERT?

I. Affected individuals are sterile females.

II. Ovaries are rudimentary.

III. They exhibit a lack of other secondary sexual characters.

IV. They are tall-statured with broad shoulders and masculine chest.
Choose the correct option:
(1)II and IV only
(2)I and II only
(3)All of the above
(4)I, II, and III
221.Assertion (A): Genetics is a branch of biology that deals with the principles of inheritance
and its practices.

Reason (R): Gregor Mendel was the first biologist to study the phenomenon of inheritance in a
purely molecular and biochemical manner in pea plants.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is true but (R) is false.
222.According to the NCERT Chapter 4 Summary, which of the following statements is/are
CORRECT regarding Mendelian principles?

I. The 'factors' regulating characters are found in pairs known as alleles.

II. In heterozygous conditions, dominant characters are expressed while recessive characters are
suppressed.

III. The dominant characters are expressed only when factors are in homozygous condition.

IV. Recessive characters can never be expressed in any filial generation.
Choose the correct option:
(1)II and IV only
(2)All of the above
(3)I and II
(4)I, II, and III
223.Assertion (A): A recessive character that is not expressed in a heterozygous F1 generation
is able to reappear completely in the homozygous F2 generation.

Reason (R): The contrasting alleles for a character never blend in a heterozygous condition, and
they segregate completely from each other during the formation of gametes.
(1)Both (A) and (R) are true and (R) is the correct explanation of (A).
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is true but (R) is false.
(4)(A) is false but (R) is true.
224.Regarding non-Mendelian exceptions and dihybrid crosses as stated in the NCERT
Summary, which of the following statements is/are CORRECT?

I. Not all characters show true dominance; some show incomplete dominance, and some show
co-dominance.

II. When Mendel studied two characters together, he found that the factors independently assort
and combine in all permutations and combinations.

III. The graphical representation of gametic combinations in a square tabular form is known as
'Punnett Square'.

IV. Punnett Square was developed by a Russian cytogeneticist named Ivan Punnett.
Choose the correct option:
(1)I and II only
(2)All of the above
(3)II and IV only
(4)I, II, and III
225.Assertion (A): A good correlation was drawn between Mendel's laws and the segregation
and assortment of chromosomes during meiosis.

Reason (R): This correlation was formally extended to propose the 'Chromosomal Theory of
Inheritance' by Sutton and Boveri.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)Both (A) and (R) are true and (R) is the correct explanation of (A).
(4)(A) is false but (R) is true.
226.According to the NCERT Chapter 4 Summary, which of the following statements is/are
CORRECT regarding linkage?

I. Mendel's law of independent assortment does not hold true for genes located on the same
chromosome.

II. These genes on the same chromosome are called 'linked genes'.

III. Closely located genes assorted together, showing tight linkage.

IV. Distantly located genes, due to recombination, assorted independently.
Choose the correct option:
(1)I, II, and III only
(2)All of the above
(3)II and IV only
(4)I and IV only
227.Assertion (A): In many organisms, the chromosomes that differ between the two sexes are
named sex chromosomes, while the remaining sets are autosomes.

Reason (R): In chicken, the male sex chromosome composition is homogametic ZZ, whereas the
female is heterogametic ZW.
(1)(A) is true but (R) is false.
(2)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(3)(A) is false but (R) is true.
(4)Both (A) and (R) are true and (R) is the correct explanation of (A).
228.Which of the following statements is/are CORRECT according to the NCERT Chapter 4
Summary regarding genetic disorders?

I. Down's syndrome, Turner's syndrome, and Klinefelter's syndrome can be easily studied by
the analysis of Karyotypes.

II. In Down's syndrome, there is an extra copy of chromosome 21, and the total chromosome
number becomes 47.

III. In Turner's syndrome, one X chromosome is missing and the sex chromosome composition is
XO.

IV. In Klinefelter's syndrome, the sex chromosome composition is XXY.
Choose the correct option:
(1)I, II, and III only
(2)I and IV only
(3)All of the above
(4)II and IV only
229.Assertion (A): Sickle-cell anemia is caused due to a change of a single base in the gene
coding for the beta-chain of hemoglobin.

Reason (R): This change represents a point mutation, which is defined as any change that
involves a whole set of chromosomes in an organism.
(1)(A) is false but (R) is true.
(2)Both (A) and (R) are true and (R) is the correct explanation of (A).
(3)Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(4)(A) is true but (R) is false.
230.Regarding chromosomal mutations as described in the NCERT Chapter 4 Summary,
which of the following is/are CORRECT?

I. Inheritable mutations can be studied by generating a pedigree of a family.

II. Some mutations involve changes in a whole set of chromosomes (polyploidy).

III. Some mutations involve changes in a subset of chromosome number (aneuploidy).

IV. Polyploidy and Aneuploidy are completely synonymous terms representing single gene
deletions.
Choose the correct option:
(1)All of the above
(2)II and IV only
(3)I and II only
(4)I, II, and III
NEET ]230[ Contd...

Answer Key

14
21
31
43
51
61
71
83
94
101
114
122
133
144
152
162
171
183
192
203
214
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231
242
252
261
271
283
293
303
311
323
331
342
353
363
372
384
392
404
412
424
433
442
452
462
473
481
493
503
511
522
531
544
552
564
571
584
593
602
611
622
633
641
651
663
671
682
694
704
712
721
731
742
754
764
774
781
791
804
811
822
834
843
854
863
873
881
892
901
912
924
932
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952
963
974
983
991
1003
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1023
1034
1044
1053
1064
1072
1084
1093
1102
1114
1122
1131
1144
1154
1164
1173
1181
1193
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1213
1224
1232
1243
1252
1261
1272
1282
1291
1302
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1323
1332
1341
1353
1363
1372
1382
1393
1404
1411
1421
1431
1441
1451
1464
1472
1481
1492
1501
1514
1522
1533
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1593
1601
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1624
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1654
1664
1672
1683
1691
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1932
1944
1951
1962
1974
1982
1993
2004
2013
2022
2031
2043
2054
2061
2071
2083
2093
2101
2114
2124
2131
2144
2151
2164
2172
2181
2192
2204
2214
2223
2231
2244
2253
2262
2272
2283
2294
2304