Lecture 14 - BIO220

Well assume you know remember this material 2 future

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Unformatted text preview: r any randomly sampled pair of nucleotides If necessary: review slides from Bio 120 (posted to portal) on measuring genetic variation and how it is maintained / generated. We’ll assume you know & remember this material. 2. Future improvement of crops – Is it possible to keep breeding better crops without genetic engineering? – Or is there insufficient genetic variation? 3. Pest and pathogen management – Can we reduce crop loss to pests? 13 14 Not branched at all Very branched Case study: Domestication of maize from teosinte Domestication led to dramatic loss of variation Genetic Diversity ( ) Maize 1:1 line •Domestication 10,000 – 5,000 ya •Application of artificial selection before discovery of genetics & natural selection Best Fit Line Genetic Diversity ( ) Teosinte EEB’s Prof. Stephen Wright Doebley and colleagues Wright et al. 2005, Science 308: 1310 1314 16 -Each dot is a locus sequenced on both the current and the ancestor (random), record the nucleotide differences -The best fit line falls below 1:1 meaning that Maize has lost its genetic diversity. the 1:1 line means no changes since domestication What does a 43% loss of variation mean ? • Can we distinguish which loci have lost variation… …because of artificial selection ? -To produce better maize versus Distinguishing bottlenecks from bottlenecks + selection • What do both bottlenecks and selection do ? • They reduce the effective population size (Ne). • Ne = The size of an idealized population with the same properties with respect to genetic drift and allele frequencies as the observed population …just because of the bottleneck ? -Bottleneck from selecting a small population size 17 18 3 04/03/2013 -In an idealized population, everyone breeds -Rate of genetic drift matches the obser ved population Effective population size Why does N Ne? • Census size (N) = total number of adults in...
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This document was uploaded on 01/27/2014.

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