Principles of Inheritance and Variation NEET PYQs (2005–2026) with Solutions

10 solved Principles of Inheritance and Variation PYQs

Real NEET and AIPMT questions from this chapter, newest first. Try each one, then open the answer and the step-by-step explanation.

1. Question 1 (NEET 2026)

   NEET 2026MediumIncomplete Dominance, Codominance, Pleiotropy and Polygenic Inheritance

   Match List I with List II: Choose the correct answer from the options given below:

   1. AOption A: A-II, B-IV, C-III, D-I
   2. BOption B: A-I, B-III, C-II, D-IV
   3. COption C: A-I, B-IV, C-III, D-II
   4. DOption D: A-II, B-I, C-III, D-IV

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   Correct answer: (A) A-II, B-IV, C-III, D-I

   Explanation

   Inheritance of flower colour in snapdragon (Antirrhinum sp.) shows incomplete dominance. ABO blood groups are examples of codominance because IA and IB express together in AB individuals. Phenylketonuria is an example of pleiotropy since one gene affects multiple phenotypic traits. Human skin colour is controlled by multiple genes, making it a case of polygenic inheritance.

2. Question 2 (NEET 2026)

   NEET 2026EasyMendelian and Chromosomal Disorders

   Which one of the following disorders is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule?

   1. AOption A: Thalassemia
   2. BOption B: Sickle-cell anaemia
   3. COption C: Phenylketonuria
   4. DOption D: Haemophilia

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   Correct answer: (B) Sickle-cell anaemia

   Explanation

   Sickle-cell anaemia results from a point mutation in the β-globin gene, causing substitution of glutamic acid by valine at the sixth position of the β-chain of haemoglobin.

3. Question 3 (NEET 2026)

   NEET 2026EasyChromosomal disorders: Down's and Turner's syndrome

   Given below are two statements : Statement I : Down’s syndrome is caused by the absence of one of the X-chromosomes. Statement II : Turner’s syndrome is caused by the presence of an additional copy of the chromosomes. In the light of the above statements, choose the correct answer from the options given below :

   1. AOption A: Both Statement I and Statement II are correct
   2. BOption B: Both Statement I and Statement II are incorrect
   3. COption C: Statement I is correct but Statement II is incorrect
   4. DOption D: Statement I is incorrect but Statement II is correct

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   Correct answer: (B) Both Statement I and Statement II are incorrect

   Explanation

   Statement I is incorrect: Down's syndrome is caused by the presence of an additional copy of chromosome number 21 (trisomy of 21), not by the absence of an X-chromosome. Statement II is incorrect: Turner's syndrome is caused by the absence of one of the X-chromosomes, i.e., 45 with XO; it is not due to an additional chromosome. The two statements have actually swapped the causes. Both are incorrect, so the answer is option (B).

4. Question 4 (NEET 2026)

   NEET 2026MediumABO Blood Group Inheritance

   What is the probability of having children with 'O' blood group, where both mother and father are heterozygous for 'A' and 'B' blood groups, respectively?

   1. AOption A: 25%
   2. BOption B: 0%
   3. COption C: 75%
   4. DOption D: 50%

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   Correct answer: (A) 25%

   Explanation

   Crossing Iᴬi × Iᴮi produces offspring: AB, A, B and O in equal proportions. Thus probability of O blood group (ii) is 25%.

5. Question 5 (NEET 2026)

   NEET 2026EasySex Determination

   In a population of grasshopper species, chromosome number of some members is 23 and some others possess 24 chromosomes. The 23 and 24 chromosome-bearing members in this species are ______.

   1. AOption A: females and males, respectively
   2. BOption B: all males
   3. COption C: males and females, respectively
   4. DOption D: all females

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   Correct answer: (C) males and females, respectively

   Explanation

   Grasshoppers exhibit XO sex determination. Males (XO) possess one fewer chromosome (23), while females (XX) have 24 chromosomes.

6. Question 6 (NEET 2026)

   NEET 2026EasyHaplodiploidy and Gamete Formation

   In which animal do haploid cells divide mitotically to produce gametes?

   1. AOption A: Male honeybees
   2. BOption B: Male earthworms
   3. COption C: Male frogs
   4. DOption D: Male grasshoppers

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   Correct answer: (A) Male honeybees

   Explanation

   Male honeybees are haploid and produce gametes through mitosis because of haplodiploid sex determination.

7. Question 7 (NEET 2026)

   NEET 2026EasyMendel's monohybrid cross and dominance

   Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : In an experiment, Mendel observed that the F1 progeny plants are all tall and none are dwarf. Reason R : Stem height is a contrasting trait, with tall being dominant and dwarf being recessive. In the light of the above statements, choose the most appropriate answer from the options given below :

   1. AOption A: Both A and R are correct and R is the correct explanation of A
   2. BOption B: Both A and R are correct but R is not the correct explanation of A
   3. COption C: A is correct but R is not correct
   4. DOption D: A is not correct but R is correct

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   Correct answer: (A) Both A and R are correct and R is the correct explanation of A

   Explanation

   When Mendel crossed true-breeding tall (TT) and dwarf (tt) pea plants, all the $F_1$ progeny (Tt) were tall, resembling one parent; none were dwarf. So A is correct. Stem height (tall vs dwarf) is one of the seven pairs of contrasting traits Mendel studied. In the heterozygote Tt, the tall allele (T) is dominant and expresses itself, while the dwarf allele (t) is recessive and is masked. So R is correct. The dominance of tall over dwarf is exactly why all $F_1$ plants are tall, so R explains A. Hence option (A).

8. Question 8 (NEET 2025)

   NEET 2025MediumRNA and DNA as Genetic Material

   Given below are two statements: Statement I : In the RNA world, RNA is considered the first genetic material evolved to carry out essential life processes. RNA acts as a genetic material and also as a catalyst for some important biochemical reactions in living systems. Being reactive, RNA is unstable. Statement II : DNA evolved from RNA and is a more stable genetic material. Its double helical strands being complementary, resist changes by evolving repair mechanism. In the light of the above statements, choose the most appropriate answer from the options given below:

   1. AOption A: Both statement I and statement II are correct
   2. BOption B: Both statement I and statement II are incorrect
   3. COption C: Statement I is correct but statement II is incorrect
   4. DOption D: Statement I is incorrect but statement II is correct

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   Correct answer: (A) Both statement I and statement II are correct

   Explanation

   RNA is believed to be the first genetic material and is chemically reactive. DNA evolved later as a more stable genetic material with repair mechanisms.

9. Question 9 (NEET 2025)

   NEET 2025EasyDeviations from Mendelism

   What is the pattern of inheritance for polygenic trait?

   1. AOption A: Mendelian inheritance pattern
   2. BOption B: Non-mendelian inheritance pattern
   3. COption C: Autosomal dominant pattern
   4. DOption D: X-linked recessive inheritance pattern

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   Correct answer: (B) Non-mendelian inheritance pattern

   Explanation

   Polygenic inheritance involves multiple genes contributing to a single trait and does not follow simple Mendelian ratios. Therefore, it is a non-Mendelian inheritance pattern.

10. Question 10 (NEET 2025)

    NEET 2025MediumMendelian Genetics

    Genes R and Y follow independent assortment. If RRYY produce round yellow seeds and rryy produce wrinkled green seeds, what will be the phenotypic ratio of the F2 generation?

    1. AOption A: Phenotypic ratio - 1 : 2 : 1
    2. BOption B: Phenotypic ratio - 3 : 1
    3. COption C: Phenotypic ratio - 9 : 3 : 3 : 1
    4. DOption D: Phenotypic ratio - 9 : 7

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    Correct answer: (C) Phenotypic ratio - 9 : 3 : 3 : 1

    Explanation

    A dihybrid cross involving two independently assorting genes produces the classical Mendelian phenotypic ratio of 9 : 3 : 3 : 1 in the F2 generation.