BIOL 2050 Lecture 7 Interaction of multiple genes

BIOL 2050 Lecture 7 Interaction of multiple genes -...

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10/2/2011 1 Interactions of multiple genes and gene expression BIOL2050 Lecture 7 Interaction of multiple genes Dominant and recessive epistatis Duplicate dominant and duplicate recessive epistatis Inheritance of DNA outside the nucleus Gene modifier epistatis Environmental gene interactions Summary Explain why different epistatic interactions give different phenotype ratios Give examples of different epistatic interactions Outline non-nuclear inheritance Describe how imprinted genes work Give examples of environmental effects on gene expression By the end of this lecture you should be able to...
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10/2/2011 2 1) Single genes 2) Multiple genes and independent assortment 3) Genes linked to sex chromosomes 4) Codominance, incomplete dominance, penetrance and lethal genes 5) Genes interacting with other genes Inheritance patterns so far... Epistasis two or more loci interact to form new phenotype Epistatis from last week... Dog coat colour Bombay phenotype Two or more loci interact to create new phenotypes - one allele masks or alters the effect of another at a different locus Epistatic gene: the gene that masks/alters Hypostatic gene: the gene that is masked/altered Epistatis definitions...
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10/2/2011 3 Coat colour controlled by Mc1R and agouti genes Coat colour in dogs Dogs have additional gene, CBD 103 , produces dominant black coat Which is the epistatic gene? Which is the hypostatic gene? Bombay phenotype Recessive mutation, h, encodes defective enzyme hh genotype cannot produce A or B antigens express O phenotype Which is the epistatic gene? Which is the hypostatic gene? Standard dihybrid cross (two traits) Epistatis and phenotype ratios
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10/2/2011 4 AaBb x AaBb Normal dihybrid cross = F 2 ratio 9:3:3:1 Recessive epistatis dihybrid cross = F 2 ratio 9:3:4 Dominant epistatis dihybrid cross = F 2 ratio 12:3:1 Epistatis and phenotype ratios Coat colour in labs Recessive epistatis and phenotype ratios Locus 1: Dominant B = black Recessive b = brown Locus 2: Dominant E = allows dark
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