Inheritance of ABO Blood Groups

ABO blood group system is an inheritable characteristic that is transmitted from parents to offspring.

The ABO blood groups have three genes involved, a case of multiple alleles and are responsible for the presence of antigen types on the Red Blood Cells.

Multiple alleles: a set of more than two alleles that may determine a character; e.g.  ABO Blood group system.

• Gene A is responsible for the presence of antigen A.
•  Gene B is responsible for the presence of antigen B.
• Gene O is responsible for no (zero) antigen on the RBCs.

The genotypes of the four blood groups in the ABO system are thus formed by allelic pairs of genes.

The marriage between a man who is heterozygous for blood group A and a woman who is heterozygous for blood group B will produce children of all four blood groups.

A man who is homozygous for blood group A married to a woman who is homozygous for blood group B would produce children who would only be AB.