PATHOLOGY

Detailed explanation-1: -Human blood type or ABO blood type is controlled by the ABO gene, which has three distinct alleles (multiple alleles), a, b, and I. The a and b alleles show a specific dominance relationship known as codominance, which means that they jointly generate the AB blood type.

Detailed explanation-2: -A polygenic trait is a characteristic, such as height or skin color, that is influenced by two or more genes. Because multiple genes are involved, polygenic traits do not follow the patterns of Mendelian inheritance.

Detailed explanation-3: -An excellent example of multiple allele inheritance is human blood type. Blood type exists as four possible phenotypes: A, B, AB, & O. There are 3 alleles for the gene that determines blood type.

Detailed explanation-4: -The gene responsible for the ABO blood group system is I. This gene exists in three allelic forms-IA, IB and i. IA and IB are dominant alleles and i is the recessive allele. Since, three alleles for ABO blood group are found in a population, it is an example of multiple allelism.

Detailed explanation-5: -An example of multiple alleles is the ABO blood group system in humans. Human gene I (I for ‘isohaemagglutinin’) exists in three allelic forms: IA, IB, and IO. IA and IB produce type A and type B antigens, respectively, on the cell surface of RBCs whereas IO (or i) is a recessive allele and does not produce antigen.