WAEC Biology 2010 Papers

Concept:ABO blood groups are controlled by three alleles: $I^A$, $I^B$, and $I^O$.Since the child has blood group O, both parents must carry the $I^O$ allele.Explanation:The child belongs to blood group O, so its genotype is $I^O I^O$.This means each parent must contribute one $I^O$ allele.Mr. Andrew has blood group A, which can be $I^A I^A$ or $I^A I^O$.To pass on $I^O$ to the child, his genotype must be $I^A I^O$.His wife has blood group B, which can be $I^B I^B$ or $I^B I^O$.To pass on $I^O$ to the child, her genotype must be $I^B I^O$.Therefore, both parents are heterozygous and carry the recessive $I^O$ allele.Answer:$I^A I^O$ and $I^B I^O$ — Option D.