 This observation is supported by the concept of a heterozygous selection coefficient operating on the HLA-DR, and at the HLA-DRB1 locus to a greater degree relative to HLA-DQB1 and HLA-DPB1.Most of the HLA alleles currently present in the human population can be explained by gene conversion between these ancient ancestral types, some that persist into the extant population.The table below provides links to subpages with information about distribution, genetic
linkage and disease association for the HLA-DR serogroups.