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Class XII · Biology

Principles of Inheritance and Variation: NEET MCQ practice

379 practice questions on Principles of Inheritance and Variation, including 67 from past NEET papers, each with an explanation. Practise them chapter by chapter in the GyaanLoop app.

379

Practice questions

208

Easy

169

Medium

2

Hard

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What Principles of Inheritance and Variation covers

Topics in the NEET (UG) 2026–27 syllabus for this chapter.

  • Mendelian inheritance
  • Deviations from Mendelism- incomplete dominance, co-dominance, multiple alleles, blood group inheritance, pleiotropy
  • Elementary idea of polygenic inheritance; chromosome theory of inheritance
  • Chromosomes and genes; sex determination in humans, birds, honey bee
  • Linkage and crossing over
  • Mendelian disorders in humans- thalassemia; chromosomal disorders- Down's, Turner's, Klinefelter's syndromes

Past NEET questions on Principles of Inheritance and Variation

Try each one, then open the answer and explanation.

Question 1 · NEET 2025

Which chromosome in the human genome has the highest number of genes?

  1. A.Chromosome X
  2. B.Chromosome Y
  3. C.Chromosome 1
  4. D.Chromosome 10
Show answer

Answer: C. Chromosome 1

Human chromosome 1 is the largest chromosome and contains around 2000-4000 genes, the highest among all chromosomes. Sex chromosomes have far fewer genes.

Question 2 · NEET 2025

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. A.Phenotypic ratio - 1 : 2 : 1
  2. B.Phenotypic ratio - 3 : 1
  3. C.Phenotypic ratio - 9 : 3 : 3 : 1
  4. D.Phenotypic ratio - 9 : 7
Show answer

Answer: C. Phenotypic ratio - 9 : 3 : 3 : 1

Independent assortment of two gene pairs with complete dominance gives a 9:3:3:1 phenotypic ratio in F2. RRYY × rryy → F1 RrYy; selfing yields classic dihybrid ratio.

Question 3 · NEET 2025

What is the pattern of inheritance for polygenic trait?

  1. A.Mendelian inheritance pattern
  2. B.Non-mendelian inheritance pattern
  3. C.Autosomal dominant pattern
  4. D.X-linked recessive inheritance pattern
Show answer

Answer: B. Non-mendelian inheritance pattern

Polygenic trait involves many genes acting together, with continuous variation, not fitting Mendel's single-gene patterns.

Question 4 · NEET 2025

Twins are born to a family that lives next door to you. The twins are a boy and a girl. Which of the following must be true?

  1. A.They are monozygotic twins.
  2. B.They are fraternal twins.
  3. C.They were conceived through in vitro fertilization.
  4. D.They have 75% identical genetic content.
Show answer

Answer: B. They are fraternal twins.

Monozygotic twins are genetically identical, so they must be the same sex. Since one is a boy and one is a girl, they cannot be monozygotic; they must be dizygotic (fraternal).

Question 5 · NEET 2024

Given below are two statements: Statement I: When many alleles of a single gene govern a character, it is called polygenic inheritance. Statement II: In Polygenic inheritance, the effect of each allele is additive. In the light of the above statements, choose the correct answer from the options given below.

  1. A.Statement I is true but Statement II is false
  2. B.Statement I is false but Statement II is true
  3. C.Both Statement I and Statement II are true
  4. D.Both Statement I and Statement II are false
Show answer

Answer: B. Statement I is false but Statement II is true

Polygenic inheritance involves multiple genes affecting one trait, not multiple alleles of a single gene. Statement I confuses 'multiple alleles' with 'multiple genes', so it is false. Statement II correctly states that in polygenic inheritance, each allele's effect is additive. Thus, I false, II true.

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