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Principles of Inheritance and Variation

38 NEET questions on Principles of Inheritance and Variation. A sample is shown below with full explanations; the rest are available free after signing up.

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Principles of Inheritance and Variation2026medium

Q1.Given below are two statements: In the light of the above statements, choose the correct answer from the options given below:

  • 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.
  • ABoth Statement I and Statement II are correct
  • BBoth Statement I and Statement II are incorrectAnswer
  • CStatement I is correct but Statement II is incorrect
  • DStatement I is incorrect but Statement II is correct

Explanation

The two statements have been swapped. Down's syndrome is trisomy 21 — an ADDITIONAL copy of chromosome 21. Turner's syndrome is the ABSENCE of one X chromosome, giving 45 chromosomes with X0. Each statement describes the other condition, so both are incorrect.

Source: NEET 2026 re-exam (21 June), Code 50, Q138

Principles of Inheritance and Variation2026hard

Q2.For a person with blood group 'O', which of the following is not a possible combination of parents' blood group genotypes?

  • AFather: IAi and Mother: IBi
  • BFather: IAi and Mother: IAi
  • CFather: IBi and Mother: IBi
  • DFather: IAIB and Mother: IAiAnswer

Explanation

A child of group O must be ii, so each parent has to carry a recessive i allele to pass on. A father of genotype IAIB carries no i at all — he can only contribute IA or IB — so that pairing cannot produce an O child. The other three parents are all heterozygous carriers.

Source: NEET 2026 re-exam (21 June), Code 50, Q169

Principles of Inheritance and Variation2026easy

Q3.Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below:

  • 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.
  • ABoth A and R are correct and R is the correct explanation of AAnswer
  • BBoth A and R are correct but R is not the correct explanation of A
  • CA is correct but R is not correct
  • DA is not correct but R is correct

Explanation

Crossing true-breeding tall with dwarf gives an F1 that is entirely Tt. Because the tall allele is dominant it masks the dwarf allele in every one of them, which is exactly why no dwarf plants appear — the reason is the explanation for the observation.

Source: NEET 2026 re-exam (21 June), Code 50, Q175

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Questions are reformatted from NEET previous year papers with original explanations and topic tagging. NEET Prep is not affiliated with the NEET examining body.