can parents with blood type a or a ab make a baby with o blood type?

Answer 1

No.
**"Type A" and "Type B" are codominant alelles (gene markers) for blood type, which means they are equally dominant over "O".
**Type A blood happens when a person either has one A marker.
**Type AB is when a person inherits one A marker and one B.
**Type O really means there are "NO" surface markers (antigens) on the red blood cells, which requires that the person inherit type O genes from BOTH parents.

So the genetics would look like this:

**Mother can be either AA or AO (both express type A)
**Father is AB (just AB)

**Therefore: Child can be AA or AB if Mother is AA; baby can be AA, AB, AO, or BO if Mother is AO. But...child cannot be Type O because OO is not a possible combination when Father is AB.♥