A man with blood group A marries with a woman with blood group O

A man with blood group A marries with a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits- blood group A or O- is dominant? Why or why not? can u explain this question with a monohybrid cross as even if the father has ao and mother has oa…in o blood group it can either be oa or oo in both cases o is dominant. Thank You

No. This information is insufficient. This is because the genotype of the parents is not given, without which we cannot predict whether the trait is dominant or recessive.

(Actually, the blood group O is recessive and A and B are the dominant blood groups, but that is something that has been understood through studies. With the information given above, we cannot deduce this)

The information on whether O is dominant or A is dominant is sufficient.

Daughter has blood group O. It must mean that she must have received an O from the father and an O from the mother.

For her to receive the O from the father then the father’s blood type must be AO since the father is blood group A and the mother’s must be OO.

We know that for a trait to be dominant we only need one gene whereas recessive traits appear when both the parents contribute recessive genes. Therefore type O blood group is a recessive type. And type A blood group is dominant.

(This is a basic check on whether the gene is dominant or recessive. There is no question of determining blood groups and it does not include any other blood group so why are there answers saying the information is insufficient. Can someone please explain?)

1 Like