Table 2: Methods for whole-genome screening.

(A) Microsatellites

These are regions in the genome that are composed of repetitive sequences. The most common microsatellites are the CA (dC-dA)n repeats. Microsatellite loci are highly polymorphic because of variation in the number of repeats (usually there are 5 to 15 alleles per locus), and they are uniformly distributed throughout the genome at distances of fewer than 1 million base pairs [15]. Therefore, microsatellites served as useful markers in linkage studies designed to search for unknown disease susceptibility genes. Investigators then further narrowed the suspected gene region with more dense markers, and the gene could be identified.

(B) Single-nucleotide polymorphisms (SNPs)

Without having to enlist families, it is now possible to use genome-wide association studies involving up to 106 SNPs (on a microchip), each of which is in linkage disequilibrium with large segments of the genome, and then analyze their association with any disease.