Minisatellites and VNTRs

Segments of DNA consisting of short tandem repeats, but in much fewer copies than satellites, are known as mini-satellites or VNTRs (Variable Number of Tandem

Repeats). Typically there may be from five to 50 tandem repeats in a VNTR. In mammals, VNTRs are common and are scattered over the genome, although they tend to be found close to the telomeres.

Due to unequal crossing over, the number of repeats in a given VNTR varies among individuals. Although VNTRs are non-coding DNA and not true genes, nonetheless the different versions are referred to as alleles. For example, Table 4.02 shows the distribution of one human VNTR of 64 bp among the population.

Some hyper-variable VNTRs may have as many as 1,000 different alleles and give unique patterns for almost every individual. This quantitative variation may be used for the identification of individuals by DNA fingerprinting.

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