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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.
- Winter '14
- Annotated Lecture S