Question

mary has type a blood. her son bill has type ab blood. which blood type does bill’s dad have if he is homozygous for blood type?
a
b
ab
o

Explanation:

Step1: Recall blood type genetics

Blood type A can be \( AA \) or \( AO \), type AB is \( AB \), and a homozygous dad has two identical alleles. Mary (A) must give an \( A \) allele. Bill (AB) gets \( A \) from Mary, so he needs \( B \) from dad. A homozygous dad with \( B \) alleles is \( BB \) (blood type B).

Step2: Eliminate other options

• Type A (homozygous \( AA \)) would give \( A \), Bill would be \( AA \) (type A), not AB.
• Type AB (homozygous \( AB \)) is heterozygous for A and B, not homozygous for a single type.
• Type O (\( OO \)) gives \( O \), Bill would be \( AO \) (type A), not AB.

Answer:

B. B