Question

The alleles for human blood types A and B are co-dominant but both are dominant over the type O allele. The Rh factor is separate from the ABO blood group and is located on a separate chromosome. The Rh-positive allele is dominant over Rh-negative. Indicate the possible phenotypes from the mating of a woman with type O Rh-negative with man with type A Rh-positive?

Answer 1

Take this question as two halves. First, deal with the ABO blood type: woman with type O mated with a man with type A. What are the possible phenotypes?
Then deal with Rh: Rh neg woman mated with Rh pos man.

Answer 2

How do I do that though? :S

Answer 3

OK, let's start with what do you know about the genotype of the woman who has type O blood?

Answer 4

If she has type O blood, is she heterozygous or homozygous for the type O allele?

Answer 5

Ahh I don't know...:/ I know heterozygous is different and homozygous is the same!

Answer 6

I'm sorry, we're doing this as an independent study and our teacher is making us learn it by ourselves...its so confusing!

Answer 7

Is it homozygous?

Answer 8

type O is recessive, so she has to be homozygous for O - she has two copies of the O allele. If she was heterozygous, such as AO, then she would be type A because A is dominant over O.

Answer 9

Yes! I get that, okay!

Answer 10

Now what about the man who is type A? What are his possible genotypes?

Answer 11

Um, he's heterozygous?

Answer 12

Yes, he could be AO, but is that the only possibility?

Answer 13

AB?

Answer 14

Since type A and type B are co-dominant, AB is type AB. He could be homozygous AA. Both AO and AA are type A blood because A is dominant over O.

Answer 15

So his possibilities would be AO and AA?

Answer 16

Yes. So the woman has to be OO, and the man could be either AO or AA - we don't know which. So what blood types could their children have if the man is AA?

Answer 17

Would we have to do a punnet square for that?

Answer 18

Yes, you can do a Punnett square. Or you could think that the woman's eggs will all have a type O allele (because the woman doesn't have any other allele), and the man's sperm will all have a type A allele (if he is AA, he doesn't have anything else). Then a type O egg fertilized by a type A sperm can only produce type AO children. Following me thus far?

Answer 19

YES! :)

Answer 20

So AO children is one possibility?

Answer 21

Yes. AO children will have type A blood. What if the man is AO? You can do a Punnett square for that mating with the OO woman.

Answer 22

okay, can i draw it on here?

Answer 23

I don't know if this allows drawing. But again all the eggs have the O allele. Half the sperm will have the A allele and half the sperm will have the O allele. So there's a 50/50 chance that the child will be AO or OO