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Insertions, substitutions, and the origin of microsatellites

Published online by Cambridge University Press:  18 January 2001

YONG ZHU
Affiliation:
Department of Ecology and Evolutionary Biology, Rice University, PO Box 1892, Houston, TX 77251–1892, USA
JOAN E. STRASSMANN
Affiliation:
Department of Ecology and Evolutionary Biology, Rice University, PO Box 1892, Houston, TX 77251–1892, USA
DAVID C. QUELLER
Affiliation:
Department of Ecology and Evolutionary Biology, Rice University, PO Box 1892, Houston, TX 77251–1892, USA

Abstract

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This paper uses data from the Human Gene Mutation Database to contrast two hypotheses for the origin of short DNA repeats: substitutions and insertions that duplicate adjacent sequences. Because substitutions are much more common than insertions, they are the dominant source of new 2-repeat loci. Insertions are rarer, but over 70% of the 2–4 base insertion mutations are duplications of adjacent sequences, and over half of these generate new repeat regions. Insertions contribute fewer new repeat loci than substitutions, but their relative importance increases rapidly with repeat number so that all new 4–5-repeat mutations come from insertions, as do all 3-repeat mutations of tetranucleotide repeats. This suggests that the process of repeat duplication that dominates microsatellite evolution at high repeat numbers is also important very early in microsatellite evolution. This result sheds light on the puzzle of the origin of short tandem repeats. It also suggests that most short insertion mutations derive from a slippage-like process during replication.

Type
Research Article
Copyright
© 2000 Cambridge University Press