7 Random genetic drift - BIO 370 Kirkpatrick Hall Fall 2004 p 1 7 Random genetic drift Random genetic drift Changes in allele frequencies caused by the

7 Random genetic drift - BIO 370 Kirkpatrick Hall Fall 2004...

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BIO 370 Kirkpatrick & Hall, Fall 2004 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 did an in-class simulation using playing cards to represent alleles 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 – there is no systematic trend • Populations that started out genetically identical became different • Genetic variation within each population was 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

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