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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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Read the chapter first

Every NCERT question in this chapter is solved, free: NCERT solutions — Principles of Inheritance and Variation →

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. The only paid thing on the site is the full-length 90-question Biology mock and its all-India rank.

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.