Jim Thomas [email protected] Foege...
Transcript of Jim Thomas [email protected] Foege...
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Jim Thomas [email protected]
Foege S340B
Slides and problem sets will be posted on the same web site…
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Weeks 6 and 7 Intro to molecular evolution - what is it? Neutral evolution and mutation Purifying selection Week 8 Phylogeny and molecular methods Deep branches Lineage sorting and hybridization, coalescent Week 9 Positive (Darwinian) selection Positive selection dN/dS methods Positive selection population methods Week 10 Positive selection examples 1 Positive selection examples 2 Connecting genotype and phenotype - the challenge
this may change
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Evolution of whales in the fossil record
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Molecular Evolution - What is it?
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2 whales
monkeys apes
rodents
cow, sheep etc
Molecular evolution - one hundred millionth (10-8) of the genomes of 68 mammals:
aardvark
bats
elephant
dog
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The two fundamentals of evolution
1) heritable variation
2) natural selection
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Heritable variation
Phenotypically familiar:
hair color hair curliness eye color ear lobes (attached or not) freckling hair line (widow's peak or not) cleft chin
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At least 10 genes, three of which have major effects: EYCL1 - green/blue alleles - chromosome 19 HERC2 - central brown ring eye color gene - chromosome 15 OCA2 - brown/blue alleles - chromosome 15 PLUS, more than 2 common alleles with functional consequences for each gene
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Molecular variation - only one kind - change in DNA sequence (or RNA for some viruses)
What about molecular variation?
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Papio hamadryas (baboon) Nomascus leucogenys (gibbon)
MRCA about 25 mYA (most recent common ancestor)
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Did the change occur in baboon or gibbon?
(other sequences are other primates, mostly from older branches)
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Natural Selection
Phenotypically familiar:
• Selection for long neck in giraffes • Selection for bill type in Darwin's finches • Selection for antibiotic resistance • Selection for camouflage coloration • Selection against sterility
etc.
What about selection on molecular variants?
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What about selection on molecular variants?
Acts via the capacity for a sequence variant to affect its own perpetuation. Recommended reading - "The Selfish Gene" by Richard Dawkins