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Question

Biology Question on Principles of Inheritance and Variation

ABO blood group system is due to

A

multifactor inheritance

B

incomplete dominance

C

multiple allelism

D

epistasis

Answer

multiple allelism

Explanation

Solution

Some genes can have more than two alleles. When a trait is controlled by more than two alleles, it is called multiple allelism. In humans, the blood group is determined by threealleles(I A, IB and IO) of a gene I. A person can only have two of the three alleles, determining his blood group. Person with both IA alleles belongs to A blood group, IAIB to AB blood group and B group for both IB alleles. Similarly, persons with O blood group have both alleles Io.

The other three options are incorrect as they do not account for the blood group in humans.

  • Multifactor Inheritance - It refers to the trait or disease caused by more than one factor like birth defect, chronic illness etc.
  • Incomplete Dominance - The condition in which the two alleles of a gene are partially expressed resulting in a different phenotype not seen in parents, is called incomplete dominance.
  • Epistasis - It is a condition in which the expression of a gene is inhibited due to the presence of another gene.