Sex-linked genes are passed on by the sex chromosomes either X or Y, depending on gender. Normally in sex-linked genes the trait is carried on the X instead of the Y, in this case either gender can be affected because males (XY) and females (XX) both carry an X chromosome. There are traits that can be carried on the Y chromosome; these only affect males since females do not carry a Y. .
The fruit flies that were used in this experiment were either white eyed or red eyed. The red-eyed trait was the wild type trait, while white eyes were the mutant trait. Wild type, red eyes, is considered dominant and mutant, white eyes, are recessive. This experiment began with two different crosses using wild type males and mutant females in one cross ad mutant males and wild type females in the second cross. These crosses were allowed to mate and reproduce making an F1 generation. The F1 generations were then allowed to mate with in themselves to produce an F2 generation. These crosses were then studied to determine if eye color is an autosomal trait or a sex-linked trait. After observing both tubes the gene that produces white eyes is found to be X linked recessive. So only females with both recessive X alleles would express white eyes and males with the one recessive X allele would express the mutant phenotype. .
Methods.
This experiment started with two different tubes that had four flies in each tube. Each tube contained media at the bottom so the drosophila had food to feed on. The flies were examined under a microscope to determine the sex of each fly. We were able to sex the flies without them flying away by putting them to sleep with fly nap. The first tube was labeled as "Cross 1" and in this tube there were two wild type, red eyed, females and two mutant, white eyed, males. The second tube was labeled "Cross 2" and it contained two mutant, white eyed, females and two wild type, red eyed, males.