how can a couple with same blood type have a child with a different type of blood type?

Question

both parents are A postive and the child is O postive? there is NO affair involved

Answer 1

if you're A type blood you can either be AA or Ai. O blood is ii. Both the parents have to have been heterozygous (Ai) for A type blood to have an O + kid:

.....A....i
A..AA..Ai
i....Ai...ii

that way there's a 25% possibility that one of their kids will be O

Answer 2

Blood type is determined by the ABO system. A and B represent two different antigens and O no antigens. A and B are co-dominant and that's how type AB comes up. Both A and B are dominant over O. So type A can be expressed by either AA or AO genotypically. The same applies for type B. In order to express type O you gotta have OO. So if the mother is of A type with a genotype of AO and father is of B type with a genotype of BO their children could actually be either one of all blood types!Hope I explained clearly enough!

Answer 3

That's easy.
If you are A+, you can have one of two genetic types- you can have one A and one O or two As.

If both parents are AO (they'd be A+) then 1/2 of their kids would be AO, 1/4 would be AA and 1/4 would be OO.

Because of the founder effect, most people in the English speaking world have some O.

Answer 4

Genetics.

Since each of us carries genes from previous generations, there is a chance that the blood type changes.

Example:

Your moms parents are A+ and O+ and she is A+
Your dads are B+ and A+ and he is A+

That means that your parents carry O+ for your mom and B+ for your dad. Since you are a product of both, then you can be either A+, B+, AB+, or 0+.

Answer 5

Recessive genes. If each parent has an A gene from one of its parents and an O from the other, then the parents can be A's, but each can give an O to the offspring.

Answer 6

Technically, you are AO+ (That's where the O comes from.)
My son is O+ and I am A+ and my husband is B-. I asked my doctor the same question, and that is what he told me.