ABSTRACT
Sequence polymorphisms are sequence variations in the human genome. One type is called a single-nucleotide polymorphism (SNP) and constitutes single base pair change originating from spontaneous mutation. SNPs can result from base substitutions, insertions, or deletions at a single site. They account for most human DNA polymorphisms. An estimated 10 million SNPs exist in the human genome and approximately 1.4 million SNPs have been identified. Most appear in noncoding regions of the genome, although some are found in coding regions as well (Figure 20.1).
