one parent is AB then they will have to hand on either an A or a B allele. If the other parent is AO the the possible combinations are AA, AB, OA, OB - this means that there's a 50% chance the child will be group A (the AA & the AO), a 25% chance the child will be AB and a 25% chance the child will be B (OB).
50%.
offspring would have type AB blood
