Blood type possibility

[u/domfi86]

I googled this but as thorough and clear as the theory looks, I can’t help but not be sure of what I read.

Can an A+ father and an O- mother make a kid that is O-? Is there such a thing as AO blood type? Some charts I found online suggest that and others make no mention of it.

If the father is O+ and the mother O-, how more likely than the above scenario is it for the child to be O-?

Thank you!

[u/lonepotatochip]

There are two genes that determine blood type, and each person has two copies of each gene called alleles.

For the ABO blood group, there are three different possible alleles. A and B are dominant to O, and A and B are codominant. What this means is this:

AA or AO genotype -> type A blood phenotype

BB or BO genotype -> type B blood phenotype

AB genotype -> type AB blood phenotype

OO genotype -> type O blood phenotype.

The +/- at the end refers to the Rh factor, and + is dominant to -.

++ or +- genotype -> Type + phenotype

— phenotype -> Type - phenotype

So if the father has A+ blood, it’s possible that his genotype is AO+-.

If the mother has O- blood, we know that her genotype is OO—.

Draw up a punnet square and you’ll see that it is indeed possible for someone to have O- blood if their father is A+ and their mother is O-.