Can 2 O positive parents have an O negative child?
Beside this, can two O positive parents have a negative child?
Depending on the parents' rH genotype (hetero/homozygous for the D-antigen), the child of two O-positive parents could be either O-positive or O-negative. The only way their child could be O-negative is if both parents are heterozygous (Dd) for the D-antigen.
Similarly, you may ask, what blood type will a child have if both parents are O positive?
Suffice it to say that A, B and AB are dominant over O, so children will be type O only if they inherit O-type genes from both parents. Children who inherit an A-O combination will be type A, but, remember, they could still pass that O gene off to their children.
The O positive mom and the O negative dad can have a child with blood type A or blood type B depending on the O negative dad's blood type. They cannot have a child with blood type O. Can a parent with O negative blood type be the biological father of a child with AB blood type (the mother is A+)?