Mapping genes in diabetes: genetic epidemiological perspective

Susceptibility to diabetes or the inherent potential to develop diabetes is controlled by genes, the hereditary elements of the cell. The identification of specific genes, which is called mapping, depends on several factors. The existence of a single major gene, genetic homogeneity (uniformity), and the availability of appropriate clinical material influence mapping the genes that determine susceptibility to diabetes. The ability to detect susceptibility genes depends on diabetic risk carried by relatives and on the location of the susceptibility genes in relation to genetic markers (which are elements that identify certain chromosomes, the threadlike structures in the cell nucleus that carry the genes). Insulin-dependent diabetes mellitus (IDDM) appears to be controlled by a single major locus, or gene site, and remaining polygenic factors, or elements with multiple gene components. The single major locus appears to consist of genes from the histocompatibility (HLA) complex, because the risk of developing IDDM seems to be controlled by specific genotypes or gene profiles. Mapping the residual polygenic factors will be a long and difficult task. The risk of developing non-insulin-dependent diabetes mellitus (NIDDM) appears to be controlled by few genes with a moderate effect and, to a greater extent, by residual polygenic factors, environmental effects, and genetic heterogeneity (variation). (Consumer Summary produced by Reliance Medical Information, Inc.)