Question

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What would be the phenotypic percentages of a cross between two parent fruit flies if the female is homozygous dominant and male has white eyes? Eye color is a sex-linked trait in fruit flies. Red is dominant over white. Draw a Punnett Square to show your work.

Answer 1

In a cross between a homozygous dominant (red-eyed) female fruit fly and a male fruit fly with white eyes, the Punnett square for a sex-linked trait would look like the above image




In this Punnett square, X^R represents the red eye allele and X^r represents the white eye allele. Y represents the Y chromosome, which determines maleness in fruit flies.

The phenotypic percentages can be determined by analyzing the genotypes produced:

50% of the offspring will be red-eyed females (X^R X^R).
50% of the offspring will be red-eyed males (X^R Y).
Since the dominant allele for red eyes is present in both the female parent (homozygous dominant) and the male parent (hemizygous dominant), all the offspring will have red eyes.

Therefore, the phenotypic percentage of red-eyed offspring would be 100% for both males and females.

Answer 2

Step-by-step explanation:

In a cross between a female fruit fly that is homozygous dominant for red eyes (XX) and a male fruit fly with white eyes (XwY), where eye color is a sex-linked trait in fruit flies, the resulting offspring can be determined using a Punnett Square.

The Punnett Square for this cross would look as follows:

| X w

-----------------

X | XX Xw

X | XX Xw

Y | XY Yw

In this case, all of the female offspring (XX) will have red eyes because they inherit a dominant red eye allele from the homozygous dominant female parent. On the other hand, the male offspring will inherit their eye color from their mother and will have a 50% chance of having red eyes (XY) and a 50% chance of having white eyes (XwY).

Therefore, the phenotypic percentages of the offspring would be:

50% of the offspring will have red eyes (females: XX, males: XY)

50% of the offspring will have white eyes (males: XwY)

It's important to note that in this case, since eye color is a sex-linked trait and the male parent has white eyes, all the male offspring will have white eyes. The red eye color allele is located on the X chromosome, and since the male offspring receive their X chromosome from their mother, they will inherit the white eye allele from their father.