THEORIES

THEORIES - THEORIES Genetics-definitions-phenotype physical...

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THEORIES Genetics -definitions -phenotype: physical characteristic -genotype: genes that influence phenotype -interacts with environment -phenotype = genotype + environment -PKU -endophenotype: measurable intermediate feature -between phenotype and genotype Family Studies -proband: person with illness -relatives: higher illness rate -genes or environment? -general population: 1% -1 st degree relative: 10% -parents, siblings, children -share 50% of genes -2 nd degree: 5% -aunts, uncles, cousins, grandparents, grandchildren -share 25% -3 rd degree: 2% -great aunts & uncles, great grandchildren -share 12.5% -lifetime risk increases with increase in genotype shared with proband -family, adoption, and twin studies consistent with genetic hypothesis Twin Studies -concordant: both twins have phenotype -both have SZ -discordant: only 1 twin has phenotype -MZ twins: identical genotypes (100% genes) -dissimilar phenotype: environmental -more than 100% concordance -not entirely genetic -DZ twins: 50% genes -assume environment same -compare MZ and DZ rates -expected MZ rate > DZ rate -genetic theory supported -5 well controlled studies -MZ rate = 46% -DZ rate = 14% -half of MZ twins don’t get SZ -same genes -environmental?
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THEORIES - THEORIES Genetics-definitions-phenotype physical...

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