WAEC Biology 2013 Papers

Concept:Blood type O is recessive and has genotype $ii$, so the boy must inherit an $i$ allele from each parent.Explanation:The mother has blood type A, so her genotype is either $I^A I^A$ or $I^A i$.Because the boy has blood type O ($ii$), the mother must have passed on an $i$ allele.Hence, the mother’s genotype is $I^A i$.The father must also give an $i$ allele to the boy.Among the given options, only genotype AO, which is $I^A i$, contains the $i$ allele.So the father cannot be BB, AA, or AB.Therefore, the father’s genotype must be AO.Answer:C. AO