5. Assume that blood type is inherited as A and B dominant over O, but A and B are codominant over each other. Genotypes (la la) and (lai) are then phenotypically type A, genotypes (le le) and
(lei) are type B, genotype (la ls) is type AB, and genotype (ii) is type O blood. A man with blood
type la la marries a woman with type AB blood. What are the genotypic and phenotypic ratios of
the children?

Genotypic ratio = 1 (IaIa) : 1 (IaIe)

Phenotypic ratio = 1 (Type A) : 1 (Type AB)

Explanation:

This question involves a single gene coding for the inheritance of blood type in humans. However, three alleles (multiple alleles) are responsible for this inheritance. Alleles ia and ie, according to the question, are dominant over alleles i.

According to this question, a man with blood type "laIa" (blood type A) marries a woman with type AB blood (IaIe). The following gametes will be produced by each parent:

IaIa - Ia and Ia

IaIe - Ia and Ie

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:

2 IaIa, and 2 IaIe offsprings

Therefore,

Genotypic ratio = 1 (IaIa) : 1 (IaIe)

Phenotypic ratio = 1 (Type A) : 1 (Type AB)