Question

a male parent has A blood group and female parent has O blood group.their offspring a girl has O blood group. can we predict which is the dominant gene or recessive gene?

Answer 1

You can always issue predictions, but in this case they will have no merit. The male could have been AO, the female OO, the offspring AO, OO, AO, or OO. Getting one offspring with O phenotype does not mean it is recessive, nor dominate.