For many diseases there exists a rich, diverse and growing literature that can be used to identify genes and chromosomal regions of high interest. This literature includes existing genetic studies of linkage and candidate genes as well as research on disease pathogenesis. For example, information about disrupted cell signaling pathways and genomic-level expression data from comparisons of tumor and normal tissues have identified interesting candidate genes for cancer. Thus investigators may have a large but finite set of genes and genomic regions that they feel deserve particular scrutiny or they may have a special interest in certain genes or chromosomal regions.
