WAEC Biology 2011 Papers

Concept:Blood group O is expressed only by genotype $ii$, and the AB parent contributes no $i$ allele.Explanation:The man of blood group AB has the genotype $I^A I^B$.The woman of blood group O has the genotype $ii$.The father can produce gametes carrying either $I^A$ or $I^B$.The mother always produces a gamete carrying $i$.Thus, the possible child genotypes are $I^A i$ and $I^B i$.So the child can only have blood group A or blood group B.No combination yields the genotype $ii$.Therefore, the probability of a child with blood group O is zero.Answer:A. 0%