Sarah has type A blood, and Jesse has type O blood. Their son has type B blood. Can Jesse be the baby daddy? He is a bit worried.

Question

Please complete the Punnett squares to determine the possibilities.

a
Yes, if one parent is heterozygous
b
No, type B blood must be homozygous
c
Yes, if both parents are heterozygous
d
No, this is impossible

Answer 1

To determine whether Jesse, who has type O blood, can be the father of a child with type B blood while Sarah has type A blood, we need to analyze the genotypes involved.

• Type A blood can be either homozygous (AA) or heterozygous (AO).
• Type O blood is always homozygous (OO).
• Type B blood can be either homozygous (BB) or heterozygous (BO).

Let's set up the possible Punnett squares:

1. If Sarah is homozygous type A (AA):

       A     A
    ----------------
    O |   AO   |   AO   |
    ----------------
    O |   AO   |   AO   |
    ----------------
   

   In this case, all the offspring would inherit AO (type A), so no children can have type B.

2. If Sarah is heterozygous type A (AO):

       A     O
    ----------------
    O |   AO   |   OO   |
    ----------------
    O |   AO   |   OO   |
    ----------------
   

   In this scenario, there is a possibility of two types of offspring:

   • AO (type A)
   • OO (type O)

No offspring can be type B in this case either.

Since Jesse has type O blood (OO) and cannot provide an allele for type B (he can only give O), the son cannot be type B if Jesse is indeed the biological father.

So the answer to your question is: d. No, this is impossible.