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lecture - cha 4-student - CHAPTER 4 Mapping Eukaryote...

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CHAPTER 4 Mapping Eukaryote Chromosomes by Recombination Copyright 2008 © W H Freeman and Company
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1. What cellular process produces a recombination of linked genes? 2. What recombinant frequencies are diagnostic of linkage? 3. How can an analysis of recombinant frequencies generate a chromosome map? 4. How are recombination maps used in conjunction with physical DNA maps? Key Questions
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What positions do genes occupy on the chromosomes? Chromosome map: Loci / locus, Distance between the loci… Recombination-based maps Physical maps
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4.1 Diagnostics of Linkage Recombination maps --- linkage analysis Using recombinant frequency to recognize linkage Completely linked Completely unlinked Test Cross No recombinant progeny 50% nonrecombinant, 50% recombinant progeny Linked with recombinant progeny
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4.1 Diagnostics of Linkage Recombination maps --- linkage analysis Using recombinant frequency to recognize linkage Linked alleles tend to be inherited together
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Crossing over produces new allelic combinations
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4.1 Diagnostics of Linkage Linkage symbolism and terminology Cis (adjacent) conformation : AB/ab or ++/ab Trans (opposite) conformation: Ab/aB or +b/a+ A B a b A b a B
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4.1 Diagnostics of Linkage Crossing over is a breakage-and-rejoining process
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4.1 Diagnostics of Linkage Crossing over takes place at the four-chromatid stage Multiple crossovers can include more than two chromatids. 4 genotypes – 4 chromatid stage after replication Between chromatids not chromosomes
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4.1 Diagnostics of Linkage Recombinants are produced by crossovers
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4.2 Mapping by Recombinant Frequency Total recombinant frequencies are less than 50 percent for linked genes. <50%
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4.2 Mapping by Recombinant Frequency Recombinant frequency = total number of recombinant progeny X 100% total number of progeny Recombinant frequency = (151 + 154) / (151 + 154 +1339 + 1195) X 100% = 305/2839 X 100% = 10.7% ≈ 11% ½ of each type -> 5.5% pr/pr .vg+/vg 10.7 % of the progeny exhibit new combinations of traits resulting from crossing over between two linked genes. F2 gametic classes: pr+ . vg+ 1339 pr . vg 1195 pr+ . vg 151 pr . vg+ 154 2839 P pr/pr · vg/vg x pr+/pr+ · vg+/vg+ Gametes pr · vg pr+ · vg+ F1 dihybrid pr+/pr · vg+/vg Testcross: pr+/pr · vg+/vg x pr/pr · vg/vg F2 progeny classes: pr+/pr . vg+/vg 1339 pr/pr . vg/vg 1195 pr+/pr . vg/vg 151 pr/pr . vg+/vg 154 2839 Biased toward parental, linked 710 709 711 708 Unlinked 1:1:1:1
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4.2 Mapping by Recombinant Frequency Recombinant frequency = total number of recombinant progeny X 100% total number of progeny Recombinant frequency = 10.7% 10.7 % of the progeny exhibit new combinations of traits resulting from crossing over between two linked genes. 10.7 m.u. The
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This note was uploaded on 11/06/2011 for the course BIL 250 taught by Professor Wang during the Fall '08 term at University of Miami.

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lecture - cha 4-student - CHAPTER 4 Mapping Eukaryote...

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