Biology Questions and Answers – Inheritance Principles – Co-Dominance

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance Principles – Co-Dominance”.

1. In what mode of inheritance, the F1 progeny exhibit characteristics of both the parents?
a) Complete dominance
b) Incomplete dominance
c) Codominance
d) Multiple allelism
View Answer

Answer: c
Explanation: Codominance refers to the equal likelihood of both alleles expressing. Thus, the progeny resembles both the parents.
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2. Which of the following is an instance of codominance?
a) Flower color in garden peas
b) Flower color in snapdragon
c) Blood grouping in humans
d) Pod color in garden peas
View Answer

Answer: c
Explanation: The ABO blood grouping in humans is an instance of codominance. Here the lack of both A and B alleles produces a new phenotype: The O blood group.

3. ABO blood grouping in humans is an instance of ___________
a) complete dominance
b) incomplete dominance
c) codominance
d) pseudoscience
View Answer

Answer: c
Explanation: Codominance refers to the production of a new phenotype when both factors that give opposing traits are present. This is observed in ABO blood grouping in humans.
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4. The ABO blood groups are determined by ______ present on RBCs.
a) proteins
b) DNA
c) RNA
d) carbohydrates
View Answer

Answer: d
Explanation: The ABO blood group is determined by the antigens present on the RBCs of a human. These antigens are sugar polymers.

5. The I gene which encodes for the blood group is a code for a sugar polymer.
a) True
b) False
View Answer

Answer: a
Explanation: The I gene is responsible for the blood group. In a complex pathway, the allele present at the locus of I gene determines the nature of the sugar polymer expressed by the RBCs. Thus indirectly, it codes for the sugar polymer.
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6. Which allele of I gene does not result in the production of any sugar antigen?
a) IA
b) IB
c) IC
d) i
View Answer

Answer: d
Explanation: The I gene codes for three antigens: IA, IB, and i. IA and IB code for sugar. The i allele does not code for any sugar.

7. The cattle coat color inheritance is an instance of _______
a) complete dominance
b) incomplete dominance
c) codominance
d) multiple allelism
View Answer

Answer: c
Explanation: The cattle coat color is an instance of codominance. Here the coat color of the progeny of parents that have contrasting coat colors has patches. Thus, both the alleles express codominantly resulting in a new phenotype.
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8. The alleles IA and IB code for the same sugar.
a) True
b) False
View Answer

Answer: b
Explanation: The genes IA and IB code for sugar. However, these sugars are slightly different. These differ in few monomers.

9. Which of the following allele is dominant over i?
a) Only IA
b) Only IB
c) Both IA and IB
d) IC
View Answer

Answer: d
Explanation: The gene I has only three alleles. These are IA, IB, and i. There is no allele as IC. Also, the alleles IA and IB are dominant over i as it does not produce any sugar.
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10. What will be the blood group of a person who has IAIB as the genotype?
a) A
b) B
c) AB
d) O
View Answer

Answer: c
Explanation: The person has two alleles IA and IB. These are codominant alleles. Thus, both of them will produce their products. Hence the person will have the blood group AB.

11. What is the ability of both IA and IB alleles to express together called?
a) Complete dominance
b) Incomplete dominance
c) Codominance
d) Multiple allelism
View Answer

Answer: c
Explanation: Codominance refers to the ability of both alleles to produce an effect even when the other is present. The alleles IA and IB are two such alleles.

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