Question

Fruit flies are X-linked for eye color. Wild type (+) is dominant to sepia (Se).

What are the expected ratios of fruit fly offspring if a heterozygous female crossed
with a sepia eyed male. Draw a Punnett square, to help determine the results.

Answer 1

The expected phenotypic ratio of the offspring is 1:1 for wild type to sepia eye color, and the genotypic ratio is 1:1 for heterozygous to hemizygous.

In fruit flies, eye color is X-linked, with wild type (+) being dominant to sepia (Se). When a heterozygous female (X^+X^Se) is crossed with a sepia-eyed male (X^SeY), the Punnett square can help determine the expected ratios of offspring.

The female's gametes:
`X^+` and
`X^{Se`

The male's gametes:
`X^{Se` and Y

Here's the Punnett square:

`X^+`
`X^{Se`

`X^{Se`
`X^+X^{Se`
`X^(Se)X^{Se`

Y
`X^+Y`
`X^(Se)Y`

The expected ratios are as follows:

1.
`X^+X^{Se` (wild type female): 1/4 or 25%

2.
`X^(Se)X^{Se` (sepia-eyed female): 1/4 or 25%

3.
`X^+Y` (wild type male): 1/4 or 25%

4.
`X^(Se)Y` (sepia-eyed male): 1/4 or 25%

Therefore, the expected phenotypic ratio of the offspring is 1:1 for wild type to sepia eye color, and the genotypic ratio is 1:1 for heterozygous to hemizygous (separated by gender).