Blood Types of Offspring: Mother B, Father A - What are the Possibilities?

If a mother has blood type B and the father has blood type A, the possible blood types of their children are A, B, AB, or O.

This is because the B allele for blood type B is dominant over the A allele for blood type A, so if the father passes on an A allele and the mother passes on a B allele, the child will have blood type AB. If the mother passes on a B allele and the father passes on an O allele, the child will have blood type B. If the mother passes on an O allele and the father passes on an A allele, the child will have blood type A. And finally, if both parents pass on an O allele, the child will have blood type O.