© 2001 AAAS
Along a 106-kilobase stretch of human chromosome 21, one study found that 18 haplotype blocks represent a segment of 147 SNPs from 20 individual copies of the chromosome. One block, containing 26 SNPs and spanning 19 kilobases, is detailed at right. The four most common haplotypes, occurring in 16 of the 20 chromosomes sampled, can be identified by two tag SNPs (bottom right). (Adapted from N. Patil, Science, 294:1719–23, 2001)
The myriad medical breakthroughs predicted to come from the sequencing of the human genome have yet to pour freely. The idea that genes related to common diseases and unique drug responses can be uncovered through careful scrutiny of genetic variation is an inspiring one, but searching for variability remains expensive and time-consuming. A project that would map variants common in most human populations might ease that search. In July 2001, five months after publication of the draft ...
