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Human Population Genetics. Human population migrations. Out of Africa, Replacement Single mother of all humans (Eve) ~150,000yr Single father of all humans (Adam) ~70,000yr Humans out of Africa ~40000 years ago replaced others (e.g., Neandertals ) Evidence: mtDNA , Y chromosome - PowerPoint PPT Presentation
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Human population migrations
• Out of Africa, Replacement– Single mother of all humans (Eve) ~150,000yr
– Single father of all humans (Adam) ~70,000yr
– Humans out of Africa ~40000 years ago replaced others (e.g., Neandertals)
– Evidence: mtDNA, Y chromosome
• Multiregional Evolution– Fossil records show a continuous change of
morphological features
– Proponents of the theory doubt mtDNA and other genetic evidence
Why humans are so similar
A small population that interbred reduced the genetic variation
Out of Africa ~ 40,000 years ago
Out of Africa
Migration of Humans
Migration of Humans
http://info.med.yale.edu/genetics/kkidd/point.html
Migration of Humans
Migration of Humans
http://info.med.yale.edu/genetics/kkidd/point.html
Human Variation in the Y Chromosome
Some Key Definitions
Mary: AGCCCGTACGJohn: AGCCCGTACGJosh: AGCCCGTACGKate: AGCCCGTACGPete: AGCCCGTACGAnne: AGCCCGTACGMimi: AGCCCGTACGMike: AGCCCTTACGOlga: AGCCCTTACGTony: AGCCCTTACG
Alleles: G, T
Major Allele: GMinor Allele: T
G/GG/GG/TG/GG/GG/GG/GT/TT/GT/G
Recombinations:At least 1/chromosomeOn average ~1/100 Mb
Linkage Disequilibrium:The degree of correlation between two SNP locations
Mom Dad
The Fall in Heterozygosity
The HapMap Project
The HapMap Project
The HapMap Project – Haplotype Blocks
The HapMap Project – LD
Fixation, Positive & Negative Selection
Neutral Drift Positive SelectionNegative Selection
How can we detect negative
selection?
How can we detect negative
selection?
How can we detect positive
selection?
How can we detect positive
selection?
Conservation and Human SNPs
CNSs have fewer SNPs
SNPs have shifted allele frequency spectra
Neutral CNS
How can we detect positive selection?
Ka/Ks ratio:Ratio of nonsynonymous tosynonymous substitutions
Very old, persistent, strong positive selection for a protein that keeps adapting
How can we detect positive selection?
EHH test
Long Haplotypes –iHS test
Some highly selected loci
Example: Microencephalin gene