Question

Hypothetically, a wild F1 female Drosophila with light eyes (lt) mothers and straw (stw) bristle fathers produced the following offspring when crossed with homozygous light-straw males: Phenotype Number light-straw 22 wild 18 light 990 straw 970 Total 2000. Compute the map distance between the light and straw loci.

1) 20 map units
2) 10 map units
3) 5 map units
4) 1 map unit
5) 2 map units

Answer 1

When a white-eyed male fruit fly is crossed with a heterozygous female for red eye color, the offspring will have a 1:1:1:1 ratio with 50% red-eyed females, 50% white-eyed females, 50% red-eyed males, and 50% white-eyed males.

Step-by-step explanation:

Eye color in Drosophila melanogaster, commonly known as fruit flies, is a classic example of an X-linked trait. The wild-type eye color is red (XW), which is dominant to white eye color (Xw). When a white-eyed male fruit fly (XwY) is crossed with a female that is heterozygous for red eye color (XWXw), the resulting offspring can be predicted using a Punnett square.

The resulting ratios for the offspring would be as follows:

• 50% of the females will have red eyes (XWXw), as they receive an XW from the mother and an Xw from the father.
• 50% of the females will have white eyes (XwXw), as they receive an Xw from each parent.
• 50% of the males will have red eyes (XWY), as they receive an XW from their mother and a Y from their father.
• 50% of the males will have white eyes (XwY), as they receive an Xw from their mother and a Y from their father.

This cross between a white-eyed male and a heterozygous female showcases a 1:1:1:1 ratio for both sexes and eye colors.