Question

A man has type A blood and his wife had type B. A physician types the blood of their four children and is amazed to find one of each blood types among them. How could this happen?

Answer 1

Blood Typing
Codominance- When both alleles are expressed at the same time Example: ABO system of blood types
This is an example that uses a 3 allele system. A person’s blood type is based on the absence or presence of certain proteins in his or her red blood cells.
A is codominant with B A is dominant over O B is dominant over O
(Neither covers the other both are expressed independently.) (Only A is expressed if A and O are present.
(Only B is expressed if B and O are present.

The four phenotypes are Type A, Type B, Type AB, and Type O

So the way it can happen is:

The type “A” parent is heterozygous and the type “B” parent is heterozygous thus they will have a 25% chance of producing each of the four phenotypes.

Answer 2

input all the children's blood types and work backwards u know that there is an A and a B in the first spot then work backwards