A person with blood type AB has the alleles I A and I B . A person with blood type O has the alleles ii . Why is it impossible for a person with blood type AB to have a child with blood type O?
A child with blood type O has to have two different alleles for this blood type.
A person with blood type AB will give a child either the I A or I B allele.
The child can have O blood if he gets the ii genotype from the other parent.
A person with blood type AB will give that same blood type to the child.