Association Studies. The Association shall furnish to the Board copies of all pertinent studies, surveys and lists which would assist the Board in making decisions.
Association Studies. Genetic association studies generally aim to narrow candidate regions, which may be chosen because on the basis of their known biological function or because they were initially identified by linkage analysis. Genetic associa- tion analysis compares allele or genotype frequencies at markers in candidate regions in affected individuals with those in unaffected individuals. An allele associated with a disease should be over-represented in affected individuals. A marker may be associated with the disease because it is a disease locus, or because one of its alleles is in linkage disequilibrium (LD) with a causal vari- ant at a disease locus. Let A and B be alleles at two distinct loci and let AB be the corresponding haplotype. A and B are said to be in LD if Pr(AB) /= Pr(A)Pr(B), with Pr(A), Pr(B) and Pr(AB) the probability of the occurrence of A, B, and AB in the population, respectively. LD suggests that two loci may be very close to one another. Disease-marker association may also be due to population admixture. This may occur if allele frequencies differ among subpopulation groups. To elimi- nate false evidence for association due to population admixture, family-based designs are used. A simple and common family-based design is the case- parent trio design, which compares the frequencies of alleles transmitted to affected individuals with those non-transmitted. For a review of family-based designs and corresponding statistical methods we refer to Xxxx (2000). In this thesis we do not consider further this type of design.
