NEET BIOLOGY

Detailed explanation-1: -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-2: -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.

Detailed explanation-3: -All other phenotypes or genotypes are considered variants of this standard, meaning that they deviate from the wild type. The variant may be recessive or dominant to the wild-type allele. An example of multiple alleles is coat color in rabbits (Figure 1). Here, four alleles exist for the c gene.

Detailed explanation-4: -The majority of human genes are thought to have more than two normal versions or alleles. Traits controlled by a single gene with more than two alleles are called multiple allele traits. An example is ABO blood type.

Detailed explanation-5: -Human blood type is determined by codominant alleles. There are three different alleles, known as IA, IB, and i. The IA and IB alleles are codominant, and the i allele is recessive. The possible human phenotypes for blood group are type A, type B, type AB, and type O.