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OJEE Principles of Inheritance and Variation — practice questions

Explore 32 free Principles of Inheritance and Variation questions in OJEE Biology. Open each question or exercise to read its content, reference answers and available explanation.

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Principles of Inheritance and Variation questions and exercises with answers

Showing questions 1–30 of 32.

Mendel conducted his hybridisation experiments on which plant?Read the answer and worked solution →Mendel selected pea plants with how many pairs of contrasting traits?Read the answer and worked solution →In Mendel's monohybrid cross between true-breeding tall (TT) and dwarf (tt) plants, the F₂ phenotypic ratio was:Read the answer and worked solution →The F₂ **genotypic** ratio in Mendel's monohybrid cross is:Read the answer and worked solution →Mendel's Law of Independent Assortment is best illustrated by the F₂ phenotypic ratio of:Read the answer and worked solution →The ABO blood-group gene (I) has how many alleles in the human population?Read the answer and worked solution →A person with blood group AB has the genotype:Read the answer and worked solution →A person with blood group O has the genotype:Read the answer and worked solution →Thomas Hunt Morgan used which model organism for his genetic studies?Read the answer and worked solution →In humans, the sex-determination mechanism is:Read the answer and worked solution →In grasshopper, the sex-determination mechanism is:Read the answer and worked solution →In birds, the sex-determination mechanism is:Read the answer and worked solution →Which of the following is a mutagen?Read the answer and worked solution →Sickle-cell anaemia is a:Read the answer and worked solution →β-Thalassemia is controlled by which gene?Read the answer and worked solution →Down's syndrome is caused by:Read the answer and worked solution →Klinefelter's syndrome is characterised by the karyotype:Read the answer and worked solution →Turner's syndrome results from the karyotype:Read the answer and worked solution →Aneuploidy refers to:Read the answer and worked solution →Polyploidy refers to:Read the answer and worked solution →In a monohybrid cross Tt × Tt, the phenotypic ratio in F2 is:Read the answer and worked solution →Genotypic ratio of a monohybrid F2 (Tt × Tt):Read the answer and worked solution →Phenotypic ratio in dihybrid F2 cross (RrYy × RrYy):Read the answer and worked solution →ABO blood groups: an individual with genotype I^A i has blood type:Read the answer and worked solution →A man with blood type AB marries a woman with blood type O. What blood types can their children have?Read the answer and worked solution →Brown eyes (B) is dominant over blue (b). Bb father × bb mother. Probability of blue-eyed child:Read the answer and worked solution →In a pedigree, a horizontal line connecting two individuals represents:Read the answer and worked solution →Pleiotropy refers to:Read the answer and worked solution →4 O'clock plant flower color shows incomplete dominance: RR (red) × rr (white) → Rr (pink). F2 phenotypic ratio (Rr × Rr):Read the answer and worked solution →Linkage map distance of 1 cM (centimorgan) corresponds to:Read the answer and worked solution →

Worked practice questions

Mendel conducted his hybridisation experiments on which plant?

  1. Antirrhinum majus (snapdragon)
  2. Pisum sativum (garden pea)
  3. Arabidopsis thaliana
  4. Drosophila melanogaster
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Correct answer: B. Pisum sativum (garden pea)

Gregor Mendel worked on **garden pea (Pisum sativum)** for 7 years (1856–1863), choosing 14 true-breeding varieties with 7 pairs of contrasting traits.

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Mendel selected pea plants with how many pairs of contrasting traits?

  1. 7
  2. 5
  3. 14
  4. 3
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Correct answer: A. 7

Mendel studied **7 pairs** of contrasting traits in pea: stem height (tall/dwarf), flower colour (violet/white), flower position (axial/terminal), pod shape (inflated/constricted), pod colour (green/yellow), seed shape (round/wrinkled), seed colour (yellow/green).

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In Mendel's monohybrid cross between true-breeding tall (TT) and dwarf (tt) plants, the F₂ phenotypic ratio was:

  1. 9:3:3:1
  2. 1:2:1
  3. 1:1
  4. 3:1 (tall:dwarf)
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Correct answer: D. 3:1 (tall:dwarf)

F₂ phenotypic ratio in a monohybrid cross = **3 tall : 1 dwarf**. Genotypic ratio = **1 TT : 2 Tt : 1 tt**. The 3:1 includes the heterozygotes Tt that look tall (dominance).

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