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BIOC16H3 (11)
Lecture 10

BIOC16 Lecture 10.pdf

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University of Toronto Scarborough
Biological Sciences
Mark Fitzpatrick

Lecture 10 Positive selection! Mcdonald krietmen test! HKA test! Evolution of new genes M-K test looked at ! Fixed! Polymorphic! ! 42! 17! ! synonymous (silent)! ! ! 7 2 Non synonymous (replacement) NF/SF = NP/ SP! Chi squared = N (ad-bc)2! (a+b)(c+d)(b+d)(a+c)! HKA test Test region! Neutral locus! Polymorphism ( variation within species)! 8! 3! ! ! ! 20 8 Divergence ( variation between species) Neutral region! Test region 2! 8! 3! Polymorphism! ! ! ! 20 19 Divergence! ! ! Will not allow any mutation at all so essential for the protein Sliding Window! - similar to a qtl! The peak tells us that we should sequence this region in a variety of individuals from population and also assess their phenotype! -predict these with increased longevity would have deft sequences in this region than those with short life spans. The origin of new genes Pagel and pomiankowski ch 3! -syllabus revised lecture schedule blackboard! - review paper on positive selection Original view was that new genes always arose from duplication! - it is not exclusive! The best way to study evolution of new genes is to first identify recently eveolved genes and then infer their origin! - drosophila -jingwei (long and langley 1993 science)! - jingwei is a fusion of two parental genes: - ymp yellow emperor and -adh! - d yakuza and d teisseri! - jingwei is -retroposition of adh mrna plus exons and introns from ymp! ! Primates-RNAselB! - new duplicate under very strong positive selection! - digestive system of leaf eating colobine monkeys (zhang et al 2002, nature genetics) RNAse1 - degrading double stranded RNA! -max efficiency at pH 7.4! -RNAse1B - max efficiency of pH 6 (pH of colobine gut) ! - 9 substitutions between 1 and 1B! -site directed mutagenesis! -7/9 substitutions found that it reduces its degrading efficiency so their thought is then... Adaptive changes have come at the expense of efficiency (relative to the ancestral form) How can we get new genes?! - Gene Duplication - whole genomes! - segmental duplication
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