Final answer:
MHC genes are diverse because they are polymorphic within the population. This polymorphism involves multiple alleles for each individual MHC locus, contributing to a very effective immune system capable of recognizing many different antigens.
Step-by-step explanation:
MHC genes are diverse because b. They are polymorphic within the population. The major histocompatibility complex (MHC) is a collection of genes coding for glycoprotein molecules expressed on the surface of all nucleated cells and is crucial for the functioning of the immune system. MHC polymorphism means that there are multiple alleles for each individual MHC locus within a population. In humans, the high level of diversity in MHC genes is represented by three highly polymorphic class I MHC genes (HLA-A, HLA-B, and HLA-C) and three class II MHC genes (DP, DQ, and DR). Due to the extensive polymorphism of these genes, it's very unlikely for a randomly chosen donor to match a recipient's MHC genotype, which includes two alleles at each locus expressed codominantly. This genetic diversity within a population is what allows the immune system to be both effective and efficient in recognizing a wide array of foreign antigens.