Chapter 10, Problem 7GP

Summary Introduction

To determine:

Which baby belongs to which couple by using the given information?

Concept introduction:

The ABO blood group is determined by three alleles of gene I: $I^A$, $I^B$ and i. The surface of red blood cells have specific surface antigens either ‘A’ or ‘B’ which are encoded by gene I. The recessive allele i does not produce any surface antigen which forms blood group O (genotype ii). If gene I encodes molecule A only, the person will have blood group A (genotype $I^{A}i$ or $I^A{I}^A$). If it encodes only molecule B, the person will have B blood group (genotype $I^B{I}^B$ or $I^{B}i$).

If gene I encodes for both molecule A and B, it give rise to blood group type AB (genotype $I^A{I}^B$). Here both $I^A$ and $I^B$ alleles are equally or codominantly expressed to give rise to a new phenotype. The person with genotype $I^A{I}^B$ will have both A and B molecules on red blood cell surface.