EVE100_221-243_2pp

EVE100_221-243_2pp - 1 221 221 Neutral theory of molecular...

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Unformatted text preview: 2/8/10 1 221 221 Neutral theory of molecular evolution How much of the genome is functionally constrained? Even synonymous sites may be under constraint 222 222 Neutral theory of molecular evolution E. coli S. cerevisiae Leucine Codon High Low High Low TTA 0.06 1.24 0.49 1.49 TTG 0.07 0.87 5.34 1.48 CTT 0.13 0.72 0.02 0.73 CTC 0.17 0.65 0.00 0.51 CTA 0.04 0.31 0.15 0.95 CTG 5.54 2.20 0.02 0.93 High and low refer to gene expression •Codon bias = non random codon usage •Mutation bias •Constraint on synonymous sites High bias, example GGG GGG GGG GGG Low bias, example GGG GGC GGA GGT 5’ 3’ 2/8/10 2 223 223 Neutral theory of molecular evolution Codon bias Ridley Commonly used codons correspond to abundant tRNAs 224 224 Neutral theory of molecular evolution Codon bias from H. Akashi The translational efFciency model for selection on codon usage 2/8/10 3 225 225 Neutral theory of molecular evolution Codon bias in multicellular organisms from Hey and Kliman 2002, Genetics Highly expressed genes (E) show greater codon bias (F) in D. melanogaster 226 226 Neutral theory of molecular evolution Codon bias in multicellular organisms Expression is correlated with codon bias in ¡ies, worms, and Arabidopsis Duret and Mouchiroud PNAS 1999 2/8/10 4 227 227 Neutral theory of molecular evolution •Codon bias is complex and is inFuenced by •Mutational bias and genetic drift •Natural selection •Gene expression...
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EVE100_221-243_2pp - 1 221 221 Neutral theory of molecular...

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