In humans, blood groups are produced by combinations of three alleles $I^A$, $I^B$ and $i$ - HSC - SSCE Biology - Question 17 - 2023 - Paper 1

Given the mother's genotype is $ii$ (blood type O) and the child's genotype is either $I^A I^A$ or $I^A i$ (blood type A), the father must contribute an $I^A$ allele. Therefore, the father's possible genotypes are:

1. $I^A I^i$ (which can produce a child with blood type A)
2. $I^A I^A$ (which can also produce a child with blood type A)
3. The father cannot have an $I^B$ allele since the mother cannot contribute the $I^B$ allele to the child.

Thus, the correct answer is:

• C. $I^A I^i$ or $I^A I^A$