Explain the genetic basis of ABO blood grouping man.

Explanation

ABO system of blood grouping in humans is based on the chemicla difference due to presence of antigens on the surface of the RBC and epithelial cells as follows :

(i) Bernstein discovered that, the inheritance of different blood group in humans is determined by a number of multiple allelic series.
(ii) THe three autosomal alleles located on chromosome 9 are concerned with determination of blood group.
(iii) The gene controlling blood type is labelled as 'L' or I. THe gene (isoagglutination) 1 exists in three allelic forms IA, IB and lo
(iv) IA specifies A antigen, IB allele determined B antigen and lo allele specifies no antigen.
(v) A child receives one fo three alkeles from each parent giving rise to six positive genotypes and four possible blood type (phenotypes)