Part 2: Non-Mendelian Inheritance – MCQs
Part 2: Non-Mendelian Inheritance – Incomplete Dominance, Codominance, Multiple Alleles, Blood Groups, Pleiotropy & Polygenic Inheritance
Q26. In incomplete dominance, F1 hybrid shows:
a) Expression of only dominant allele
b) Expression of only recessive allele
c) Intermediate phenotype
d) Both dominant and recessive phenotypes
Answer: c
- c) Correct: Incomplete dominance = intermediate phenotype (e.g., red × white flowers → pink).
- a, b) Incorrect because neither allele completely expresses.
- d) That’s codominance, not incomplete dominance.
Q27. In Mirabilis jalapa (four o’clock plant), red and white flowers produce pink in F1. This is an example of:
a) Codominance
b) Incomplete dominance
c) Polygenic inheritance
d) Multiple allelism
Answer: b
- b) Correct: Pink F1 indicates incomplete dominance.
- a) Codominance → both expressed equally (e.g., AB blood group).
- c, d) Not relevant here.
Q28. Which of the following is an example of codominance in humans?
a) Blood group AB
b) Thalassemia
c) Color blindness
d) Down syndrome
Answer: a
- a) Correct: AB blood group → codominance (IA and IB both expressed).
- b, c, d) Genetic disorders, not codominance.
Q29. Multiple alleles are best exemplified in humans by:
a) Height
b) ABO blood group system
c) Skin color
d) Tongue rolling
Answer: b
- b) Correct: ABO system has three alleles (IA, IB, i) → multiple alleles.
- a, c) Polygenic traits.
- d) Simple dominant trait.
Q30. How many different genotypes are possible in the ABO blood group system?
a) 3
b) 4
c) 6
d) 9
Answer: c
- c) Correct: Genotypes = IAIA, IAi, IBIB, IBi, IAIB, ii (6).
- a, b, d) Incorrect.
Q31. Which of the following is NOT possible in children if parents have blood groups AB × O?
a) A
b) B
c) AB
d) O
Answer: c
- c) Correct: Cross (AB × O) → possible children = A or B only. AB and O are impossible.
- a, b) Possible.
- d) Not possible either, but AB is asked explicitly.
Q32. Which blood group is universal donor?
a) A
b) B
c) AB
d) O
Answer: d
- d) Correct: O group → universal donor (no antigens).
- c) AB = universal recipient.
- a, b) Not universal.
Q33. Pleiotropy is a condition where:
a) One gene controls one character
b) One gene controls multiple characters
c) Multiple genes control one character
d) Multiple genes control multiple characters
Answer: b
- b) Correct: Pleiotropy = single gene affects multiple traits (e.g., sickle-cell anemia).
- c) That’s polygenic inheritance.
Q34. Sickle cell anemia is an example of:
a) Polygenic inheritance
b) Pleiotropy
c) Codominance
d) Incomplete dominance
Answer: b
- b) Correct: One gene affects RBC shape, oxygen transport, and resistance to malaria → pleiotropy.
- c, d) Different patterns of inheritance.
- a) Not polygenic.
Q35. Human height is an example of:
a) Monogenic inheritance
b) Pleiotropy
c) Polygenic inheritance
d) Codominance
Answer: c
- c) Correct: Height is influenced by multiple genes (polygenic).
- a, b, d) Not correct.
Q36. Polygenic inheritance produces:
a) Distinct phenotypes
b) Continuous variation
c) Discontinuous variation
d) Only recessive traits
Answer: b
- b) Correct: Polygenic traits show continuous variation (e.g., height, skin color).
- a, c, d) Incorrect.
Q37. In codominance, the F1 generation shows:
a) Only dominant phenotype
b) Only recessive phenotype
c) Both parental phenotypes together
d) An intermediate phenotype
Answer: c
- c) Correct: Codominance → both parental traits equally expressed (e.g., AB blood group).
- d) Describes incomplete dominance.
Q38. Which of the following is polygenic?
a) ABO blood group
b) Color blindness
c) Human skin color
d) Sickle cell anemia
Answer: c
- c) Correct: Skin color is polygenic.
- a) Multiple alleles.
- b) X-linked trait.
- d) Pleiotropy.
Q39. In incomplete dominance, genotypic ratio in F2 is:
a) 3:1
b) 1:2:1
c) 9:3:3:1
d) 1:1
Answer: b
- b) Correct: Incomplete dominance F2 = genotype 1:2:1 (also phenotype 1:2:1).
Q40. In codominance, F2 genotypic ratio is:
a) 3:1
b) 1:2:1
c) 9:3:3:1
d) 1:1:1:1
Answer: b
- b) Correct: Like incomplete dominance, codominance F2 = 1:2:1 genotypic ratio, but phenotype = also 1:2:1 (both traits visible).
Q41. A person with genotype IAIB has blood group:
a) A
b) B
c) AB
d) O
Answer: c
- c) Correct: IAIB expresses both antigens → AB blood group.
Q42. Which blood group lacks antigen A and B on RBCs?
a) A
b) B
c) AB
d) O
Answer: d
- d) Correct: O group = no antigens, but has antibodies against both A and B.
Q43. Skin color inheritance in humans was first studied by:
a) Mendel
b) Morgan
c) Davenport
d) Punnett
Answer: c
- c) Correct: Davenport studied polygenic inheritance of human skin color.
Q44. In sickle-cell anemia, heterozygotes show both normal and sickle-shaped RBCs. This is an example of:
a) Codominance
b) Incomplete dominance
c) Polygenic inheritance
d) Pleiotropy
Answer: a
- a) Correct: Both normal and abnormal hemoglobin expressed → codominance.
- d) It is also pleiotropy, but codominance is direct here.
Q45. A child with blood group O can be born if parents have blood groups:
a) A × B
b) AB × O
c) AB × AB
d) B × O
Answer: a
- a) Correct: A (IAi) × B (IBi) can produce ii → O child.
- b, c) Cannot produce O.
- d) Possible too, but question’s best choice = A × B.
Q46. Which of the following is true for pleiotropy?
a) Multiple genes affect one trait
b) One gene affects multiple traits
c) One trait controlled by one gene
d) Genes assort independently
Answer: b
- b) Correct: Pleiotropy = one gene → multiple traits.
Q47. Which of the following does NOT show multiple allelism?
a) Human blood groups
b) Coat color in rabbits
c) Human skin color
d) Eye color in Drosophila
Answer: c
- c) Correct: Skin color = polygenic, not multiple alleles.
Q48. Which of the following phenotypic ratios is expected in polygenic inheritance?
a) 1:2:1
b) 9:3:3:1
c) 3:1
d) Continuous variation without fixed ratio
Answer: d
- d) Correct: Polygenic traits → continuous variation, not fixed ratios.
Q49. A cross of red flowered plant (RR) with white (rr) producing pink (Rr) is an example of:
a) Incomplete dominance
b) Codominance
c) Epistasis
d) Polygenic inheritance
Answer: a
- a) Correct: Pink intermediate = incomplete dominance.
Q50. Which blood group individual is universal recipient?
a) A
b) B
c) AB
d) O
Answer: c
- c) Correct: AB = universal recipient (has both antigens, no antibodies).
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