Assignment 6

1 .		To understand how recombination frequencies can be used to determine an approximate map distance between closely linked genes, work within FlyLab and cross a female fly with the eyeless mutation for eye shape with a male fly with shaven bristles. Both of these genes are located on chromosome IV in Drosophila. Testcross one of the F1 females to a male with both the eyeless and shaven bristle traits. The testcross progeny with both mutations or neither mutation (wild-type) are produced by crossing over in the double heterozygous F1 female. The percentage of these recombinant phenotypes is an estimate of the map distance between these two genes. Enter the percentages of the recombinant phenotypes below. You can also draw a map on paper that shows the map distance (in map units or centimorgans) between the locus for the shaven bristle allele and the locus for the eyeless allele.
2 .		To understand how recombination frequencies can be used to determine a genetic map for three alleles, mate a female fly with a black body, purple eyes, and vestigial wing size to a wild-type male. These three alleles are located on chromosome III in Drosophila. Testcross one of the F1 females to a male with all three mutations. The flies with the least frequent phenotypes should show the same phenotypes; these complementary flies represent double crossovers. What is the phenotype of these flies? What does this tell you about the position of the purple eye allele compared with the black body and vestigial wing alleles? You can also sketch a genetic map on paper indicating the relative loci for each of these three alleles, and indicate the approximate map distance between each locus.