In Drosophila , the breeding of a red-eyed female ( X w+ , X w+ ) fruit fly with
ID: 227279 • Letter: I
Question
In Drosophila, the breeding of a red-eyed female (Xw+,Xw+) fruit fly with a white-eyed male fruit fly (XwY) produces male and female offspring that only have red eyes. When these F1 red-eyed females and red-eyed males are mated, approximately 50% of offspring are red-eyed females, 25% red-eyed males and 25% white-eyed males. Based on these results, indicate if the following statements are true or false.
1. Eye color is found on the Y chromosome. TrueFalse
2. Eye color is found on the X chromosome. TrueFalse
3. White eye color is dominant over red eye color. TrueFalse
4. Red eye color is dominant over white eye color. TrueFalse
5. Eye color inheritance is independent of the sex of individuals. TrueFalse
6. Eye color is an example of sex-linked inheritance. TrueFalse
Explanation / Answer
1. Eye color is found on the Y chromosome. False
2. Eye color is found on the X chromosome. True
3. White eye color is dominant over red eye color. False
4. Red eye color is dominant over white eye color. True
5. Eye color inheritance is independent of the sex of individuals. True
6. Eye color is an example of sex-linked inheritance. True
Explanation:
In Drosophila the locus for eye color is located on the X chromosome.
The allele for red eye color, which is normal in wild flies, is dominant to the mutant allele for white eyes.
As females have two chromosomes X (with a locus for eye color), they might be homozygous or heterozygous for either allele.
Males, who carry only one X chromosome, are always hemizygous. They carry only the one X chromosome inherited from their mother, and it determines their eye color.