ABSTRACT
Nearly all diseases are believed to have a genetic component, even those caused by infectious agents or other environmental elements. The host genome may influence disease susceptibility, the rate of disease progression, the risk of specific outcomes, or the response to therapy. The identification of a large number of single nucleotide polymorphisms (SNPs) across the genome, and the development of technology capable of typing large number of markers, has opened the possibility of performing genome wide scans with SNPs. The genome SNP scan strategy depends on linkage disequilibrium associations between phenotype-causing variants and flanking markers. Prevailing thought is that most variants that contribute to common diseases will have a low relative risk and will be frequent in the population. Direct gene analysis is an approach that is well suited for finding rare alleles that cause diseases. In this approach DNA from affected individuals is scanned for variations in functional candidate genes.
