Question

For human blood type, if you cross a parent that has a heterozygous A blood type and a parent with O blood type, what are the possible blood types of their offspring? (Show Punnett square)

Answer 1

When working with blood types, we're gonna use the letter I. Both A and B are dominants over O (as O means the absence of A and B) and they also can present codominance between each other (if one allele of each is found, both will be equally expressed). So, as we have the blood types A, B, AB and O, they are represented by:

A - Iᴬ Iᴬ (homozygous) or Iᴬ i (heterozygous)

B - Iᴮ Iᴮ (homozygous) or Iᴮ i (heterozygous)

AB - Iᴬ Iᴮ (codominance)

O - i i (recessive)

Now we must cross a heterozygous A (Iᴬ i) with a O (i i) in a Punnett square, as follows:

As we can see:

- 2/4 (or 50%) of the offspring would possibly be Iᴬ i (heterozygous A blood type)

- 2/4 (or 50%) of the offspring would possibly be i i (O blood type)