Effect of population associations and reduced penetrance on observed and expected genotype frequencies in a simple genetic model: application to HLA and insulin dependent diabetes mellitus.
The observed and Hardy--Weinberg-expected frequencies for (HLA) marker heterozygotes in a disease population are calculated where it is assumed that the disease is caused by either homozygosity or heterozygosity (with reduced pentrance) for a disease susceptibility allele at a disease locus, that allele being positively associated with both of the relevant alleles at the marker locus (the single susceptibility allele model of Svejgaard & Ryder, 1981). It is shown that the observed frequency is always less than or equal to the H-W expectation, with the (observed/expected) ratio decreasing as the degree of dominance increases.
D000483:Alleles; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics*; D004198:Disease Susceptibility; D005787:Gene Frequency; D005802:Genes, MHC Class II; D008040:Genetic Linkage; D005828:Genetics, Population; D005838:Genotype; D006680:HLA Antigens / Q000235:genetics*; D006684:HLA-DR Antigens; D006801:Humans; D008957:Models, Genetic
D006680:HLA Antigens; D006684:HLA-DR Antigens