WAEC Biology 2011 Papers

Concept:The child inherits one allele from each parent, and the $I^A$ allele is dominant over the $I^O$ allele.Explanation:The father has genotype $I^A I^A$, so he always passes on an $I^A$ allele.The mother has genotype $I^A I^O$, so she can pass on either $I^A$ or $I^O$.Thus, the possible genotypes of their child are $I^A I^A$ and $I^A I^O$.Both genotypes produce blood group $\mathrm{A}$, because $I^A$ dominates $I^O$.Since every possible child genotype contains at least one $I^A$ allele, the son will express blood group $\mathrm{A}$.Answer:The blood group of their son is likely to be $\mathrm{A}$.