Question

In the ABO blood type system the IA and IB alleles:

Select one:
a. Are recessive
b. Are codominant
c. Are both expressed when both are present
d. Both A and C are correct
e. Both B and C are correct

Answer 1

The IA and IB alleles in the ABO blood type system are codominant and both are expressed when present together, resulting in AB blood type. The i allele is recessive and results in type O blood when present in a pair (ii).

Step-by-step explanation:

In the ABO blood type system, the IA and IB alleles are codominant.

This means that both alleles are expressed equally when they are present together in an individual's genotype, leading to the AB blood type. When a person has genotype IAIB, both the A and B antigens are present on the surface of red blood cells.

In contrast, the allele i, which results in the O blood type, is recessive and will not be expressed if either IA or IB alleles are present.

In the case where i is paired with i (ii), the individual will have the O blood type, as no antigen is produced. Genotypes for type A blood could be IAIA (homozygous) or IAi (heterozygous), and for type B blood could be IBIB (homozygous) or IBi (heterozygous).