Microsatellites Introduction The Human Genom

Microsatellites are short sequences of repetitive DNA that are tandemly repeated and qualitatively similar, and are important in gene mapping (Hancock, 1996, p. 191). Other simple short sequences exist, but are not repeated tandemly. Microsatellites are widespread in the human genome. Many microsatellites occur as mono- and dinucleotides, where (A/T)n is the most common motif. Microsatellites containing strings of A bases also dominate the frequency distribution of longer motif satellites.

This review will look at some properties of microsatellites and at some of the information about the human genome that can be gained from the study of microsatellites, what they can tell us about the evolution of mankind, and how they can be used to examine the genetic basis of disease.

Microsatellites are often used as markers in studying the evolution of disease (Macauba, Jin, Hallmayer, Kimura and Mignot, 1997). These researchers looked at the mutation pattern of the microsatellites DQCAR, located in the HLA

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n will require the use of additional microsatellite loci and diallelic genetic markers with lower mutation rates. This type of study was carried further by Seielstad, Bekele, Ibrahim, Toure and Traore (1998). Genetic evidence suggests that all modern humans share a recent common ancestor of African origin The three lines of evidence for this are that most genetic loci examined so far show greater diversity in African populations than in others; place the first branch between African and non-African populations in phylogenetic trees; and indicate recent dates for either the molecular coalescence or the time of separation between African and non-African populations. These researchers analyzed variations at 10 Y chromosome microsatellite loci that were typed in 506 males representing 49 populations and every inhabited continent. This exhaustive study revealed significantly greater Y chromosome diversity in Africa than anywhere else; that the first branch of the phylogenetic trees of the continental populations fell between Africa and all non-African populations, and the branching was dated with the (sigma mu)2 distance measure to 5800-17,400 or 12,800-36,800 years BP, depending on the mutation used. These results demonstrate
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