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Proc Natl Acad Sci U S A. 2007 Dec 11;104(50):19926-30. Epub 2007 Dec 4.

Genetic drift at expanding frontiers promotes gene segregation.

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  • 1Department of Physics and FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA.

Abstract

Competition between random genetic drift and natural selection play a central role in evolution: Whereas nonbeneficial mutations often prevail in small populations by chance, mutations that sweep through large populations typically confer a selective advantage. Here, however, we observe chance effects during range expansions that dramatically alter the gene pool even in large microbial populations. Initially well mixed populations of two fluorescently labeled strains of Escherichia coli develop well defined, sector-like regions with fractal boundaries in expanding colonies. The formation of these regions is driven by random fluctuations that originate in a thin band of pioneers at the expanding frontier. A comparison of bacterial and yeast colonies (Saccharomyces cerevisiae) suggests that this large-scale genetic sectoring is a generic phenomenon that may provide a detectable footprint of past range expansions.

PMID:
18056799
[PubMed - indexed for MEDLINE]
PMCID:
PMC2148399
Free PMC Article
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