Workshop 3: linkage analysis
For each of the crosses listed below:
(1) mate the parent flies exactly as shown
(2) backcross the F1 females back to the parent male and note down the F2 phenotype numbers
(3) hypothesise what you expect the genotypic and phenotypic outcomes for the F1 backcross will be. Assume independent assortment and show expected ratios of genotypes and phenotypes.
(4) Note the numbers of F2 progeny next to your hypothetical outcome and do a chi square test to see if they are different
(5) determine which phenotypes are parental and which are recombinant
(6) calculate the recombination frequency between the loci by dividing the sum of the F2 recombinant phenotypes by the total number of F2 progeny and multiplying by 100 (ie, express this figure as a percentage). This number is called the map distance and a percent = a centimorgan. Thus a recombination frequency of 33% is also a map distance of 33 centimorgans.
The crosses are:
wild type female x purple eyes and apterous wings male
wild type female x sepia eyes and spineless bristles male
wild type female x radius incomplete and spineless bristles male
wild type female x brown eyes and dumpy wings male
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