04BIS10110152013RecombinLect4

Three recessive x linked genes in drosophilia scscute

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Unformatted text preview: 2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 28 3 Approaches to Constructing Genetic Maps ­ Approach 1. Determining gene order using multiple, two factor crosses involving Determining overlapping loci. Gene order will be revealed by consistent map distances. overlapping BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 29 3 Factor Test Cross without Double Crossovers ­ Approach 2. Perform a 3-factor test cross (F1 x tester) and determine genetic distances first. As above, gene order will be revealed by consistent map distances between the three loci. This approach can be performed without rare double crossover progeny. crossover 3-Factor Crosses without double crossovers (data from Bridges and Olbrycht, 1925). Three recessive X-linked genes in Drosophilia: sc=scute; ec=echinus; genes Drosophilia sc=scute; ec=echinus; cv=crossveinless cv F1 + + ec X sc cv ec sc cv + BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez tester 30 3 Factor Test Cross without Double Crossovers F1 + + ec X sc cv ec tester sc cv + Progeny Phenotypes + + ec 810 sc cv + 828 + cv + 88 sc + ec 62 + cv ec 89 sc + + 103 1980 Parental Phenotype 3 2 + sc + cv ec + 1 Compare recombination between 3 pairs of loci (1, 2 and 3) 1. 2. sc-cv 88+62+89+103 = 342/1980 X 100 = 17.3% cv-ec 89+103 = 192/1980 X 100 = 9.7% 3. sc-ec 88+62 = 150/1980 X 100 = 7.6% BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 31 3 Factor Test Cross without Double Crossovers 1. 2. sc-cv 88+62+89+103 = 342/1980 X 100 = 17.3% cv-ec 89+103 = 192/1980 X 100 = 9.7% 3. sc-ec 88+62 = 150/1980 X 100 = 7.6% Begin mapping with closest loci 7.6 ec sc By adding the third locus, 2 alternative maps emerge 9.7 7.6 or 17.3 7.6 cv sc cv ec sc Correct ec 9.7 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 32 Tomato Trihybrid Cross with D...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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