Microsatellite Instability


Microsatellites are a ubiquitous component of the genome of higher organisms. Their high mutation rate provides the basis for the successful use of microsatellites as genetic markers. Exceptionally long microsatellites have been found to be associated with certain human genetic diseases.

Keywords: microsatellite; DNA replication slippage; trinucleotide expansion

Figure 1.

Microsatellite terminology.

Figure 2.

Model of deoxyribonucleic acid (DNA) slippage, (a) adding or (b) removing one repeat unit. (1) First round of DNA replication. (2) DNA slippage, causing one repeat unit to loop out (the direction of DNA slippage is indicated in green). (3) DNA synthesis continues without repair of the loop. (4) Second round of DNA replication leads to addition or deletion of one repeat unit in one of the DNA strands.

Figure 3.

Deoxyribonucleic acid (DNA) slippage model for the expansion of a trinucleotide repeat. (1) First round of DNA replication. (2) Transient dissociation of DNA strands. (3) DNA slippage and hairpin formation. (4) DNA replication continues. (5) Expanded repeat after second round of DNA replication.

Figure 4.

Okazaki fragment procession model. (1) First round of deoxyribonucleic acid (DNA) replication (synthesis of the lagging strand). (2) Okazaki fragment displacement by DNA polymerase (the Okazaki fragment is marked with an asterisk). (3) DNA slippage and hairpin formation of the trinucleotide repeat located in the Okazaki fragment. The hairpin is resistant to flap endonuclease (FEN) 1 processing. (4) Upstream and downstream Okazaki fragments are joined. (5) Expanded repeat after second round of DNA replication.


Further Reading

Goldstein DB and Pollock DD (1997) Launching microsatellites: a review of mutation processes and methods of phylogenetic inference. Journal of Heredity 88: 335–342.

Goldstein D and Schlötterer C (1999) Microsatellites. Oxford: Oxford University Press.

Ellegren H (2000) Microsatellite mutations in the germline: implications for evolutionary inference. Trends in Genetics 16: 551–558.

Harr B, Todorova J and Schlötterer C (2002) Mismatch repair driven mutational bias in D. Melanogaster. Molecular Cell 10: 199–205.

Schlötterer C (1998) Microsatellites. In: Hoelzel RA (ed.) Molecular Genetic Analysis of Populations: A Practical Approach, 2nd edn, pp. 237–261. Oxford: Oxford University Press.

Schlötterer C (2000) Evolutionary dynamics of microsatellite DNA. Chromosoma 109: 365–371.

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Schlötterer, Christian, and Harr, Bettina(Mar 2004) Microsatellite Instability. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0000840]