AP BIOLOGY

Detailed explanation-1: -"In fruit flies, eye color is a sex-linked trait: Red is dominant to white. What are the sexes and eye colors of flies with the following genotypes: XRX’ XRY-XX: XRXR: d. XY : What are the genotypes of these flies: White eyed male: White eyed, female: red eyed female (heterozygous): d.

Detailed explanation-2: -In fruit flies, the gene for eye color is carried on the X chromosome which is a sex chromosome (sex-linked). The allele for red eyes is dominant over the allele for white eyes. If a white-eyed female fruit fly is mated with a red-eyed male, predict the possible offspring.

Detailed explanation-3: -The eye color gene is located on the X chromosome (one of the sex determining chromosomes of Drosophila). White eye color is recessive. When a red eyed male mates with white eyed females, their daughters will have red eyes, but their sons will have white eyes.

Detailed explanation-4: -Sex Determination in Drosophila The balance between female-determining factors encoded on the X chromosome and male-determining factors encoded on the autosomes determines which sex-specific pattern of transcription will be initiated. Thus, XX, XXY, and XXYY flies are females, while XY and XO flies are males.

Detailed explanation-5: -Normally, flies have either one or two X chromosomes and two sets of autosomes. If there is but one X chromosome in a diploid cell (1X:2A), the fly is male. If there are two X chromosomes in a diploid cell (2X:2A), the fly is female (Bridges 1921, 1925). Thus, XO Drosophila are sterile males.