Question

A child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.

Answer 1

$I^A$i $I^B$i	$I^A$	i
$I^B$	$I^A$$I^B$ (AB blood group)	$I^B$i (B blood group)
i	$I^A$i (A blood group)	ii (O blood group)

To have a child with O blood group, both paretns should have atleast one copy of i allele. This means parents with A and B blood group are heterozygous and have genotype $I^A$i and $I^B$i respectively. Parental genotypes $I^A$i and $I^B$i give progeny with 1 $I^A$$I^B$: 1$I^B$i: 1 $I^A$i : 1 ii genotypic ratio.