2. Multiple Alleles and Dominance: In human red blood cells, there are 3 alleles

Question

2. Multiple Alleles and Dominance: In human red blood cells, there are 3 alleles for the gene

that codes for surface carbohydrates A, B, or O (no carbohydrate). Let’s assume that A and B

are codominant with respect to one another and A and B both dominate over O.

a. What are the phenotypes of the following genotypes: AO, BO, AB, OO.

b. A man with type B marries a woman with type A. They have 6 children, 2 are AB, 1

is A, 2 are B and one is O.

i. What are the genotypes of the parents?

c. The child with type O marries a person with type AB.

i. What is the probability that they will have a child with type AB? With A?

With O?

d. A man with type B marries a woman with type A. They have one child with type AB

and 2 with type B. What are the genotypes of the parents?

Explanation / Answer

a] AO - A blood group, BO - B group, AB - AB group , OO - O group.

b] i- Since they have all blood groups in the children, it means they have all three alleles coming from the parents. That's why man is BO and woman is AO.

c] OO * AB will give AO / BO offsprings.

i - Child with AB is 0% chance, A has 50% chance and O again has 0% chance.

d - Since the children are B and AB, the parents can be with either - AO & BO or AA & BO or AO & BB.

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