In fruit flies, the color of the eyes is sex linked (on the X chromosome). Complete the cross of the flies in the image to determine the possible offspring produced (Homozygous white eyed female x red eyed male). Red eyes are dominant (R), White eyes are recessive (r). What percentage of the female offspring are expected to have red eyes? a 100% b 75% c 50% d 25% e 0%

Answer 1

To determine the percentage of female offspring with red eyes from a cross between a homozygous white-eyed female and a red-eyed male, we need to analyze the genotypes of the parents.

• The homozygous white-eyed female has the genotype X^rX^r (where X^r is the X chromosome with the recessive white eye allele).
• The red-eyed male has the genotype X^RY (where X^R is the X chromosome with the dominant red eye allele).

Now let's set up the Punnett square for the offspring:

       X^R     Y
    ----------------
X^r |  X^rX^R | X^rY |
X^r |  X^rX^R | X^rY |

From the Punnett square, we can see the potential genotypes of the offspring:

1. X^rX^R (female with red eyes)
2. X^rY (male with white eyes)

The female offspring genotype is X^rX^R, which has red eyes due to the presence of the dominant allele (X^R).

Calculating percentages:

• 2 females with X^rX^R (red-eyed).
• Therefore, 100% of female offspring will have red eyes.

Thus, the answer is a 100%.