Genetics of Complex Diseases

Abstract

In recent years, the emphasis in the field of human disease gene mapping has shifted towards the isolation of genes involved in complex diseases. Complex diseases are characterized as those traits that run in families and are commonly found in the population, but do not exhibit a simple mode of inheritance. They are often referred to as multifactorial because evidence suggests that complex diseases are caused by more than one gene, likely in combination with environmental factors. Screening efforts to identify genes for complex diseases appear complicated when considering that the risk for developing these disorders may depend on a particular combination of susceptibility alleles in many unlinked genes, with the effect of a single locus being small. Recent reports have described efforts to identify genes for multiple sclerosis (, , , ), rheumatoid arthritis () and obesity (, , , ). Other than the insulin gene for type 1 diabetes (, , , ) and apolipoprotein E for late-onset Alzheimer’s disease (, , ), few genes have been confirmed to have a functional role in the etiology of complex human disease. However, newer developments in molecular methodologies make the prospects of finding complex disease genes more likely.