Lecture Notes 8

Lecture Notes 8 - Lecture 8 1/31/2008 Biosc 0350 Genetics...

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Lecture 8 1/31/2008 1 Biosc 0350 Genetics Lecture 8 - Mapping in eukaryotes (1) l Chromosomal theory of inheritance l • review nondisjunction • hallmarks of sex-linked genes Inheritance of genes on the same chromosome • Linkage on autosomes - use of testcross • Linkage on X chromosome χ 2 test for linkage Meiotic recombination due to crossing over 1/31/08 Martens. Biosc 0350, University of Pittsburgh 2 Rare mistakes in meiosis provided further support Rare mistakes in meiosis provided further support for chromosome theory for chromosome theory Calvin Bridges: Repeated Morgan’s cross (white-eyed females x red-eyed males) in large scale Surprise! 1/2000 males 1/2000 females Hartwell et al , 3rd ed. Fig. 4.20
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Lecture 8 1/31/2008 2 1/31/08 Martens. Biosc 0350, University of Pittsburgh 3 Rare mistakes in meiosis provided further support Rare mistakes in meiosis provided further support for chromosome theory for chromosome theory Bridges hypothesis: Nondisjunction Supported by cytological studies showing rare white- eyed females were indeed XXY. Transmission of white allele followed predicted behaviour of X chromosome Hartwell et al , 3rd ed. Fig. 4.21 1/31/08 Martens. Biosc 0350, University of Pittsburgh 4 Rare mistakes in meiosis provided further support Rare mistakes in meiosis provided further support for chromosome theory for chromosome theory Bridges correctly predicted segregation in an XXY female Hartwell et al , 3rd ed. Fig. 4.21
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Lecture 8 1/31/2008 3 1/31/08 Martens. Biosc 0350, University of Pittsburgh 5 Hallmarks of X and Y linked traits in humans • males more likely to exhibit trait • affected male always have male offspring who are not affected • rare affected females have affected sons • affected male usually has daughters who are carriers
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Lecture Notes 8 - Lecture 8 1/31/2008 Biosc 0350 Genetics...

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