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Lecture 23

BIOLOGY 1M03 Lecture Notes - Lecture 23: Population Genetics, Epistasis, PhenylketonuriaPremium


Department
Biology
Course Code
BIOLOGY 1M03
Professor
Jon Stone
Lecture
23

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BIOLOGY1M03Lecture23HumanPopulationGenetics
RegulatoryChanges:
● Mostofthedifferencesbetweenhumansandchimpsaredrivenbyregulation.
○ Wehavethesamegenes,butweexpressthelonger,atdifferenttimes,
more,less,etc…
● HAR1istheregionthathasthemostchangesbetweenhumansandchimps,and
isassociatedwithregulatingaproteininthebrain.
● Duplicationofgenesisarandomevent,andalargemutation.Ifthereare
multiplecopiesofthisgene,moreproteinscanbemade.Itisdifficulttodetect
thembecauseDNAissequencedbyrandomslicesofDNAinthegenomeis
“stitched”together,andtheonlywaytoknowisbeserendipitous.
● ItispossibletounderstandregulationbytakinglivetissueandtakingoutRNA,
whichismoredirect,andcomparingit.
● TheMcDonaldKreitmantestcomparesnumberswhichusesynonymousand
nonsynonymouschangesinordertodetectpositive,negative,orneutral
selection.
HumanNeanderthalDifferences:
● Detectingthedifferencebetweenhumansandneanderthalsismuchmore
difficult.
● Itiseasiertocomparetwospecieswithasmallerdivergence.
● Comparingthedifferencesbetweengenomesdoesnotcomparethemechanisms
behindthegenomes.
PopulationGeneticQuestions:
● Whatmaintainsdeleteriousallelesis
○ Adeleteriousalleleisamutationthatis“bad”forus,oradefectthat
lowersfitnessrelativetothewildtype/variantoftheallelethatmostofus
have
● GeneTraitAssociation:Ifaparticularmarker,alleleX,isfoundinpeoplewith
traitY,itmaybeassociated.
● MechanisticArgument:Ifaparticularmarker,alleleX,producesaproteinthat
doesZ,thenitcanbeinferredthatadefectinalleleXwillleadtoproblemswithZ
● GeneEnvironmentAssociation:Ifaparticularmarker,alleleX,isfoundin
environmentA
● GeographicVariationinDiversity:Ifaparticularmarker,alleleXismorevariable
inlocationB
○ Consideringitsvariation
○ Thelongeragenelastsinapopulation,themorevariableitwillbe
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