Blood Groups

The ABO blood group is controlled by three alleles (the different forms of a gene that occupy the same locus on homologous chromosomes and produce contrasting characteristics) namely A, B, O. A is dominant to O, B is also dominant to O, but A and B are co-dominant. Each of the blood groups in humans is the result of a combination of any two of the three alleles (A, B and O) According to the ABO system of classifying human blood, there are four blood groups, which are A, B, AB, and O. each person belongs to one of these four groups. Blood groups are hereditary. When more that two alleles influence one character, as with these blood groups , they are described as multiple alleles. However, only two of the alleles may occupy the same locus of homologous chromosome in a particular individual The knowledge of blood group is used: • To predict the possible blood group of children of couples • To settle legal questions relating to paternity • As a basis for blood transfusions