Worked problems answers

Worked problems answers - Worked problems Question 1 Genes...

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Unformatted text preview: Worked problems: Question 1: Genes a and b are linked, with 10% recombination. What would be the phenotypes, and the probability of each, among progeny of the following cross? a b+ a+ b X ab ab recombinants: a b / a b : 10% / 2 = 5% a+ b+ / a b b : 10% / 2 = 5% parentals: a b+ / a b : 90% / 2 = 45% a+ b / a b : 90% / 2 = 45% Question 2: Genes a and b are sec-linked and are located 7 mu apart on the X-chromosome of Drosophila. A female of genotype a+ b / a b+ is mated with a wildtype male (a+ b+/ Y). a) What is the probability that her sons will be a+ b+ in phenotype? b) What is the probability that her daughters will be a+ b+ in phenotype? a) a+ b+ / Y = recombinant; frequency = 7% / 2 = 3.5% b) a+ b+/ any genotype from mother ; 100% a+ b + phenotype Question 3: In corn, the allele for coloured (C) seeds is dominant to the allele for colourless (c). A gene controlling endosperm development shows a similar relationship, Full (S) is dominant to shrunken (s). You are not sure what the parental phenotypes were, but you have the following F1 progeny: Coloured, full 4 032 Coloured, shrunken 149 Colouless, full 152 Colourless, shrunken 4 035 Total 8 368 Are these genes linked? If so, construct a linkage map. Yes; 3.6 mu between c and s Question 4. A corn plant known to be heterozygous at three loci is testcrossed. The progeny phenotypes and numbers are as follows: +++ abc +b c a ++ ++c ab+ +b+ a+c 455 470 35 33 37 35 460 475 Give the gene arrangement, linkage relationships, and map distances. b is sorting independently of a and c, that is why we see a c with b or b+ with equal frequency i.e. a c b and a c + with equal frequency, + + b and + + + with equal frequency. (RF=50% between b and a and b and c) Recombinants between a and c = 140/1860 = 7.5% a --- 7.5mu --- c b on a different chromosome or very far away on the same chromosome. ...
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This note was uploaded on 06/09/2011 for the course BIOLOGY 2c03 taught by Professor Dej during the Spring '11 term at McMaster University.

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Worked problems answers - Worked problems Question 1 Genes...

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