Small differences in DNA sequence are thought to account for the wide variation between people. In the November 23
They set out to map a large number of common single nucleotide polymorphisms (SNPs) on human chromosome 21 and to define their haplotype structure. They took a panel of 24 individuals and used a rodent-human somatic cell hybrid technique to separate each person's two copies of chromosome 21.
Patil et al. constructed high-density oligonucleotide arrays corresponding to 21.6 Mb of non-repetitive sequence from chromosome 21 (3.4 x 109 oligonucleotides) and screened 20 independent copies of chromosome 21. They did this by generating 3253 long-range PCR products for each sample; in this way they could map almost 36,000 SNPs. They found that the SNPs occurred in blocks ...
