Part 1: Mendelian Inheritance and Basic Genetic Principles (25 MCQs)
Part 1: Mendelian Inheritance and Basic Genetic Principles (25 MCQs)
Q1. Mendel is known as the father of genetics because:
a) He discovered DNA structure
b) He proposed the laws of inheritance through pea plant experiments
c) He discovered chromosomes
d) He discovered mutations
Answer: b
- b) Correct: Mendel studied pea plants and established the laws of inheritance, making him the father of genetics.
- a) Wrong: DNA structure was discovered by Watson and Crick.
- c) Wrong: Chromosomes were discovered by Waldeyer.
- d) Wrong: Mutation concept was introduced by Hugo de Vries.
Q2. Mendel selected pea plants for his experiments mainly because:
a) They were perennial and slow to grow
b) They showed distinct contrasting traits
c) They had a large genome
d) They reproduced only by cross-pollination
Answer: b
- b) Correct: Mendel chose pea plants because they showed clear contrasting traits (like tall/dwarf, yellow/green seeds).
- a) Wrong: They were annual, not perennial.
- c) Wrong: Genome size wasn’t the reason.
- d) Wrong: Pea plants are naturally self-pollinating, not cross-pollinating.
Q3. The ratio 3:1 in Mendel’s monohybrid cross is observed in:
a) Genotypic ratio of F2 generation
b) Phenotypic ratio of F1 generation
c) Phenotypic ratio of F2 generation
d) Genotypic ratio of F1 generation
Answer: c
- c) Correct: In a monohybrid cross, F2 shows 3:1 phenotypic ratio (3 dominant : 1 recessive).
- a) Wrong: Genotypic ratio in F2 is 1:2:1.
- b & d) Wrong: F1 generation shows uniform phenotype, not 3:1.
Q4. Which of the following is NOT a Mendelian principle?
a) Law of dominance
b) Law of segregation
c) Law of independent assortment
d) Law of linkage
Answer: d
- d) Correct: Linkage was discovered later by Morgan, not part of Mendel’s laws.
- a, b, c) Correct Mendelian principles.
Q5. In a monohybrid cross, the F1 offspring are always:
a) Heterozygous
b) Homozygous dominant
c) Homozygous recessive
d) Any of the above
Answer: a
- a) Correct: F1 from cross between homozygous dominant and homozygous recessive → heterozygous.
- b, c) Wrong: Only one parent is homozygous.
- d) Wrong: Not random, always heterozygous.
Q6. The genotypic ratio 1:2:1 in Mendelian cross represents:
a) Incomplete dominance
b) Monohybrid cross F2
c) Codominance
d) Dihybrid cross
Answer: b
- b) Correct: In a monohybrid F2, genotype ratio = 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive.
- a) In incomplete dominance, phenotype also shows 1:2:1.
- c, d) Not correct.
Q7. A test cross involves crossing:
a) F1 hybrid × recessive parent
b) F1 hybrid × dominant parent
c) Dominant × dominant
d) Recessive × recessive
Answer: a
- a) Correct: Test cross = cross of unknown dominant genotype with recessive parent.
- b, c, d) Do not define test cross.
Q8. The physical expression of a gene is called:
a) Genotype
b) Phenotype
c) Allele
d) Trait
Answer: b
- b) Correct: Phenotype = observable characteristics.
- a) Genotype = genetic constitution.
- c) Allele = variant of a gene.
- d) Trait = feature determined by gene but phenotype is visible expression.
Q9. The law of segregation states that:
a) Genes separate without blending
b) Alleles of a pair separate during gamete formation
c) Dominant gene always suppresses recessive
d) Genes assort independently
Answer: b
- b) Correct: Alleles separate during gamete formation (Mendel’s first law).
- a) Too general.
- c) This is law of dominance.
- d) Independent assortment is separate law.
Q10. Which of the following traits in pea is recessive?
a) Tall plant
b) Green seed color
c) Round seed shape
d) Yellow seed color
Answer: b
- b) Correct: Green seed color is recessive, yellow is dominant.
- a, c, d) Dominant traits.
Q11. A dihybrid cross produces how many types of gametes?
a) 2
b) 4
c) 8
d) 16
Answer: b
- b) Correct: For AaBb → 4 gametes (AB, Ab, aB, ab).
- a, c, d) Incorrect.
Q12. Independent assortment can be explained by:
a) Monohybrid cross
b) Dihybrid cross
c) Test cross
d) Back cross
Answer: b
- b) Correct: Independent assortment is evident from dihybrid cross (9:3:3:1 ratio).
- a, c, d) Not applicable.
Q13. The phenotypic ratio 9:3:3:1 is observed in:
a) Monohybrid cross
b) Test cross
c) Dihybrid cross F2
d) Back cross
Answer: c
- c) Correct: Classic Mendelian dihybrid cross → 9:3:3:1 phenotypic ratio.
Q14. Pure lines are obtained by:
a) Cross-pollination
b) Self-pollination
c) Back cross
d) Mutation
Answer: b
- b) Correct: Repeated self-pollination maintains homozygosity → pure lines.
- a, c, d) Do not guarantee pure lines.
Q15. Which of the following is an example of dihybrid inheritance?
a) Tall × dwarf
b) Round yellow × wrinkled green
c) Red × white flower
d) Color blindness inheritance
Answer: b
- b) Correct: Round yellow × wrinkled green shows two traits → dihybrid cross.
- a, c) Monohybrid.
- d) Sex-linked inheritance, not dihybrid.
Q16. In Mendel’s experiments, which generation was uniform in phenotype?
a) P generation
b) F1 generation
c) F2 generation
d) F3 generation
Answer: b
- b) Correct: F1 was uniform due to dominance.
- a, c, d) Show variation.
Q17. Which of the following is a contrasting pair of characters studied by Mendel?
a) Yellow and green seeds
b) Blue and red flowers
c) Smooth and hairy stems
d) Tall and short leaves
Answer: a
- a) Correct: Yellow vs. green seed was one of Mendel’s seven traits.
- b, c, d) Not studied by Mendel.
Q18. The character which appears in the F1 generation is called:
a) Recessive
b) Dominant
c) Lethal
d) Homozygous
Answer: b
- b) Correct: Dominant traits express in F1.
- a, c, d) Not correct.
Q19. Which of the following correctly represents Mendel’s dihybrid test cross ratio?
a) 9:3:3:1
b) 1:1:1:1
c) 1:2:1
d) 3:1
Answer: b
- b) Correct: Dihybrid test cross → 1:1:1:1.
- a, c, d) Incorrect ratios.
Q20. What is the probability of producing a homozygous recessive in a monohybrid cross?
a) 0%
b) 25%
c) 50%
d) 75%
Answer: b
- b) Correct: In Aa × Aa → 1/4 aa (25%).
- a, c, d) Incorrect.
Q21. In dihybrid cross, how many phenotypes are produced in F2?
a) 2
b) 4
c) 8
d) 16
Answer: b
- b) Correct: Four phenotypes (round yellow, round green, wrinkled yellow, wrinkled green).
- a, c, d) Wrong counts.
Q22. Which of the following is NOT a Mendelian trait in pea plants?
a) Seed color
b) Pod shape
c) Leaf shape
d) Plant height
Answer: c
- c) Correct: Leaf shape was not studied by Mendel.
- a, b, d) Mendelian traits.
Q23. If both alleles are identical, the condition is called:
a) Heterozygous
b) Homozygous
c) Hemizygous
d) Codominant
Answer: b
- b) Correct: Homozygous = same alleles.
- a) Heterozygous = different alleles.
- c) Hemizygous = single allele (e.g., X-linked in males).
- d) Codominant refers to expression, not allele identity.
Q24. A cross between an individual with unknown dominant genotype and homozygous recessive is known as:
a) Test cross
b) Back cross
c) Reciprocal cross
d) Hybrid cross
Answer: a
- a) Correct: This is test cross.
- b) Back cross = F1 × parent.
- c, d) Not specific here.
Q25. Mendel’s work was rediscovered in 1900 by:
a) Morgan, Watson, Crick
b) Hugo de Vries, Correns, Tschermak
c) Darwin and Wallace
d) Bateson and Sutton
Answer: b
- b) Correct: Rediscovered independently by Hugo de Vries, Correns, and Tschermak.
- a, c, d) Incorrect combinations.
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