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NEET · Biology · Class 12

Principles of Inheritance and Variation — NEET Biology MCQs

30 questions written by hand against the NCERT chapter. Every wrong option is explained, not just the right one.

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Sample questions from this chapter

A pea line self-pollinates for many generations and continues producing the same trait. What property made it useful to Mendel?
  1. It is true-breeding and has stable homozygous inheritance ✓
  2. It produces a new allele in each generation
  3. It prevents gamete formation
  4. It expresses both contrasting traits in each plant
Answer: A. True-breeding lines preserve a trait through repeated selfing because relevant alleles are homozygous. Crossing contrasting stable parents makes the hybrid result interpretable.
Why not B: Frequent new mutation would obscure rather than clarify transmission patterns.
Why not C: A breeding line must make gametes and progeny for crosses.
Why not D: The selected parental lines showed one stable member of each contrasting pair.
A violet-flowered plant of unknown genotype is test-crossed with vv. Half the offspring are violet and half white. What is the unknown genotype?
  1. Homozygous dominant, VV
  2. Homozygous recessive, vv
  3. Heterozygous, Vv ✓
  4. Either VV or Vv with equal probability
Answer: C. A 1:1 test-cross result comes from V and v gametes of a heterozygote meeting only v tester gametes. The cross converts an invisible allele into a visible offspring class.
Why not A: VV crossed with vv produces uniformly Vv violet progeny.
Why not B: A vv plant would display the recessive white phenotype.
Why not D: The observed recessive offspring directly demonstrate that the unknown supplied v.
Selfing a dihybrid gives 9 individuals with one phenotype and 7 with another, rather than four Mendelian classes. Which interaction best explains the 9:7 ratio?
  1. Complementary gene action requiring a dominant allele at both loci for the first phenotype ✓
  2. Dominant epistasis in which one allele masks the second locus
  3. Complete linkage producing only parental phenotypes
  4. Codominance at one ABO-like locus
Answer: A. The 9 class contains A_B_, where both pathway steps function; A_bb, aaB_ and aabb all fail one or both steps and combine as 7. The deviation reveals gene interaction rather than failed segregation.
Why not B: Dominant epistasis classically combines classes into a 12:3:1 ratio.
Why not C: Complete linkage in a coupling-phase self does not generate the characteristic complementary 9 versus 7 grouping.
Why not D: One-locus codominance gives heterozygote expression, not a modified dihybrid ratio.

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Other NEET Biology chapters

The Living WorldBiological ClassificationPlant KingdomAnimal KingdomMorphology of Flowering PlantsAnatomy of Flowering Plants

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Questions

How many NEET questions are there on Principles of Inheritance and Variation?

This chapter test has 30 questions — 10 easy, 14 medium and 6 hard — all written against the NCERT Class 12 chapter.

Is this NEET Biology chapter test free?

Yes. Every chapter test is free with no login, and you get your all-India rank on every one. Nothing on the site is on sale right now.

Do the questions explain the wrong options?

Yes — every distractor carries its own explanation naming the specific misconception that makes a student pick it. That is the part most question banks skip, and it is the part that changes your next attempt.