Question

In humans, the "A" allele codes for Type A blood, the "B" allele codes for Type B blood, and the "o" allele codes for Type O blood. "A" and "B" are both dominant to "o." A and B are codominant to each other.

What is the genotypic ratio of a cross between a mother who is heterozygous Type A and a father who is heterozygous Type B?

A. 1 AB : 1 A0:1 Bo : 1oo

B. All AB

C. 2 AA: 2 BB

D. 1 Ao: 2 00:1 Bo​

Answer 1

Heterozygous means having two different alleles.
The A allele and B allele are dominant. This means that they will be the main allele to express itself. If someone has an A and an o allele, which is recessive, the A allele would express itself over the o allele. A and B are codominant - meaning that if someone had both A and B alleles they’d have type AB blood, as they’d both express.

The mother is heterozygous type A - that means she has one A allele and one o allele
The father is heterozygous type B - meaning he has one B allele and one o allele. I know that it is Bo because if it was BA then he’d have type AB blood because the A and B alleles are codominant.

The genotype ratio is a ratio saying what the chances are of having one type of something (ex blood type, eye color) given the alleles of parents. To find this out make a punnet square with A o on top and B o on the side. Fill it in. I’ve attached a pic of what it will look like.

As you can see 1/4 is AB, 1/4 is Ao, 1/4 is Bo and 1/4 is oo. So the ratio will be letter A: AB:Ao:Bo:oo