Gene is a stretch of a DNA that determines a particular trait. Genes can mutate and take two or more alternative forms, now these are called alleles of a particular gene. Now allele occurs in a fixed spot in a chromosome and in humans we have two sets of chromosomes. Every person has a unique pattern of traits made up of their interests, values, abilities and personality characteristics, these traits can be objectively identified and profiled to represent an individual’s potential. Every occupation is made up of factors required for the successful performance of that occupation. These factors can be objectively identified and represented as an occupational profile.

The blood group characteristic in humans is controlled by three set of alleles, namely, IA, IB, and i. The alleles, IA and IB, are equally dominant whereas allele, i, is recessive to the other alleles. The individuals with genotype, IA IA and IA i, have blood group A whereas the individuals with genotype, IB IB and IB i, have blood group B. The persons with genotype IA IB have blood group AB while those with blood group O have genotype ii. Hence, if the father has blood group A and mother has blood group B, then the possible genotype of the parents will be

Father Mother

IA IA or IA i IB IB or IB i

A cross between homozygous parents will produce progeny with AB blood group.

A cross between heterozygous parents will produce progenies with AB blood group (IAIB) and O blood group (ii).