In fruit flies, eye color is a sex-linked trait. Red is dominant to white.

Question

What are the sexes and eye colors of flies with the following genotypes:

(4 points)
Male with red eyes Female with Red eyes Male with white eyes Female with white eyes








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Answer 1

In fruit flies (Drosophila melanogaster), the gene for eye color is located on the X chromosome, which makes it a sex-linked trait. The inheritance of this trait can be understood by examining the genotype of the flies.

1. Male with red eyes:

   • Genotype: X\(^R\)Y (where X\(^R\) is the X chromosome carrying the dominant red eye allele)
   • Sex: Male
   • Eye Color: Red

2. Female with red eyes:

   • Genotype: X\(^R\)X\(^R\) or X\(^R\)X\(^W\) (X\(^W\) being the X chromosome carrying the white eye allele, but X\(^R\) is dominant)
   • Sex: Female
   • Eye Color: Red

3. Male with white eyes:

   • Genotype: X\(^W\)Y (X\(^W\) is the X chromosome carrying the white eye allele)
   • Sex: Male
   • Eye Color: White

4. Female with white eyes:

   • Genotype: X\(^W\)X\(^W\)
   • Sex: Female
   • Eye Color: White

In summary:

• Male with red eyes: Male, Red
• Female with red eyes: Female, Red
• Male with white eyes: Male, White
• Female with white eyes: Female, White