Microsatellite

A microsatellite is a tract of repetitive DNA that consists of a particular sequence of base pairs repeated a large number of times. Microsatellites occur at thousands of locations within an organism's genome. They have a higher mutation rate than other areas of DNA leading to high genetic diversity. Microsatellites are often referred to as short tandem repeats (STRs) by forensic geneticists and in genetic genealogy, or as simple sequence repeats (SSRs) by plant geneticists.

Microsatellites and their longer cousins, the minisatellites, together are classified as VNTR (variable number of tandem repeats) DNA. The name "satellite" DNA refers to the early observation that centrifugation of genomic DNA in a test tube separates a prominent layer of bulk DNA from accompanying "satellite" layers of repetitive DNA.

They are widely used for DNA profiling in cancer diagnosis, in kinship analysis (especially paternity testing) and in forensic identification. They are also used in genetic linkage analysis to locate a gene or a mutation responsible for a given trait or disease. Microsatellites are also used in population genetics to measure levels of relatedness between subspecies, groups and individuals.

History

Although the first microsatellite was characterised in 1984 at the University of Leicester by Weller, Jeffreys and colleagues as a polymorphic GGAT repeat in the human myoglobin gene, the term "microsatellite" was introduced later, in 1989, by Litt and Luty. The increasing availability of DNA amplification by PCR at the beginning of the 1990s triggered a large number of studies using the amplification of microsatellites as genetic markers for forensic medicine, for paternity testing, and for positional cloning to find the gene underlying a trait or disease. Prominent early applications include the identifications by microsatellite genotyping of the eight-year-old skeletal remains of a British murder victim (Hagelberg et al.