Genetics problem: Mom is heterozygous for type A blood and Dad is homozygous for type B blood. The chance that their child will have type AB blood is:
A)0%
B)25%
C)50%
D)100%

Question

Quizplus · Accepted Answer

The child will inherit one allele from each parent. The possible combinations are:
- AB (one allele from mom is A and one allele from dad is B)
- A (one allele from mom is A and one allele from dad is either B or O)
- B (one allele from dad is B and one allele from mom is either A or O)
- O (one allele from mom is O and one allele from dad is O)

Since mom has an A allele and a B allele, she can pass down either one to her child with equal probability. Dad has only B alleles, so he can only pass down a B allele to his child. Therefore, the possible blood types for their child are AB and B. The chance of the child having AB blood is 50%.

Genetics Problem: Mom Is Heterozygous for Type a Blood and Dad