Restructuring Human Variation

Following the sequencing of the human genome in 2001, genetic variation between people was largely pinned on simple sequence differences known as single-nucleotide polymorphisms, or SNPs. This led to large-scale SNP-mapping ventures, such as the International HapMap Project, to identify regions of the genome underlying phenotypic variation and disease susceptibility. But SNPs are only part of the picture. Recently, scientists are realizing that structural differences - including deletions, duplications, inversions, and copy-number variants - encompass millions of bases of DNA, and are at least as important as SNPs in contributing to genomic variation in humans.