The human genome contains large numbers of repetitive DNA sequences, some of which are arrayed as tandem repeat units. Polymorphic tandem repeats occur in two general families: VNTRs and STRs. VNTR or minisatellite DNA consists of variable numbers of a repeating unit from 15 to 100 nucleotides long.
The repeated unit in STR or microsatellite DNA ranges from two to six bases. Products of different lengths can be amplified by using primers complementary to conserved sequences flanking the tandem repeat regions; the length of each amplification product is directly proportional to the number of repeats.
These amplification products can be resolved to individual alleles by CGE. Thus, a person can have at most two different alleles, one from each chromosome. Laser-induced fluorescence detection of fluorescence-labeled PCR products and multicolor analysis enable the rapid generation of multilocus DNA profiles.
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