7) Random genetic drift - BIO 370 Mark Kirkpatrick Instructor p 1 7 Random genetic drift Random genetic drift Changes in allele frequencies caused by

7) Random genetic drift - BIO 370 Mark Kirkpatrick...

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BIO 370 Mark Kirkpatrick, Instructor p. 1 7. Random genetic drift Random genetic drift: Changes in allele frequencies caused by the random sampling of genes The principle was not known to Darwin, but was worked out by Sewell Wright and others in the 20 th century We discovered several features of drift using: 1) a simulation in class (playing cards represented alleles in 3 populations each with 2 individuals) 2) looking at results of computer simulations 3) looking at results of an experiment using Drosophila We saw: • Drift causes evolutionary change in the absence of selection • Allele frequencies are equally likely to go up or down – no systematic trend • Populations that start out genetically identical became different • Genetic variation within each population is eventually lost (one allele or the other will become fixed) • Looking backward in time, one consequence of drift is that all copies of a gene descend from a single common ancestral copy of that gene

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