If both parents are blood Type A could they have a child with O?

Yes, it is possible for a couple with blood type A to have a child with blood type O. People who have type A blood have A antigens on the surface of their red blood cells, and they produce anti-B antibodies in their plasma. People with type O blood have neither A nor B antigens on their red blood cells, and they produce both anti-A and anti-B antibodies in their plasma.

If both parents have type A blood, they each have a 50% chance of passing on the A allele and a 50% chance of passing on the O allele. If they both pass on the O allele, their child will have type O blood.

Here is a Punnett square that shows the possible genotypes and phenotypes of a couple with type A blood:

| | A | O |

|:---:|:---:|:---:|

|A| AA (A) | AO (A)|

|O| AO (A)| OO (O)|

As you can see from the Punnett square, there is a 25% chance that a couple with type A blood will have a child with type O blood.