The ruby (r) and the crossveinless (cv) genes of Drosophila are linked, and are located on the X chromosome at map positions 7.5 and 13.7, respectively. Suppose that male fruit flies with ruby eyes and crossveinless wings (recessive traits) are mated to homozygous females with wild type red eyes and wild type wings. Their F1 daughters were collected and mated to ruby, crossveinless “tester” males.
- Write out the genotypes of the male and female parents and their F1 male and female offspring. [2 pts.]
- Based on the known map positions of the r and cv genes, what phenotypes are expected among the F2 offspring produced by the F1 females and tester males? [1.5 pts.]
- How many of each phenotypic class would you predict if 1000 F2 offspring were scored? [1.5 pts.]