Genetics PP10 (Chapter 7)

Very similar experiment same results c crossing over

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Unformatted text preview: urs at 4-chromatid stage C. of meiosis of x Only 2 out of 4 chromatids in tetrad Only participate in any given Xover participate III. Predicting Crosses With Linked Genes III. s s A. Recombination Frequency RF = Proportion of recombination-type RF offspring from a cross offspring E.g. cucumbers -- texture linked to glossiness RF = 16%, so we predict that the two RF recombinant types of offspring will each be 8% of the total of III. Predicting Crosses With Linked Genes III. B. Testcross of F1 double heterozygote reveals B. more than intercross more s Estimate the number of recombinations in Estimate meiosis of heterozygous parent by looking at progeny progeny x Gamete Gamete from F1 parent determines progeny phenotype (other parent is double recessive) x Count Count number of recombinant offspring and divide by total to get recombination frequency divide RF = (10 + 10) / 100 = 20% III. Predicting Crosses With Linked Genes III. s Remember -- only 2 chromatids take part in a Remember crossover, so only 2/4 products per meiosis are recombinant are s One recomb. event --> 2 reciprocal classes of One recomb. progeny recomb. IV. Multiple Crossovers IV. A. Double crossovers 1. Can be a second Xover between same 1. 2 chromatids that already have had one Xover Xover s Rare compared to single Xover x Requires 2 simultaneous independent Requires events, so P(Double Xover) = P(1st Xover) X P(2nd Xover) P(1st IV. Multiple Crossovers IV. A. Double crossovers 1. Can be a second Xover between same 1. 2 chromatids that already have had one Xover Xover Rare compared to single Xover Rare x Requires 2 simultaneous independent Requires events, so P(Double Xover) = P(1st Xover) X P(2nd Xover) P(1st s 2. Can have 2 Xovers involving 3 or 4 chromatids -- much rarer still chromatids...
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This note was uploaded on 09/27/2013 for the course BIO 342 taught by Professor Susanhoffman during the Fall '13 term at Miami University.

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