Question

One possibility for your white eyed male flies (white fly lines) is that they contain the white (w) mutant allele, which is located on the X chromosome. Write out: a. (1pt) the genotypes of the parental generation, assuming you crossed a male fly that is hemizygous for white (w) with a true breeding, wild-type female. You can use the shortened notation for all the parts below. b. (1pt) What are the expected genotypes and phenotypes in the F1 generation after you perform the parental cross in part a of this question. c. (1pt) Next you cross your F1 males to your F1 females. Write the Punnett square showing the genotypes expected in the F2 progeny. d. (0.5pt) Write out the phenotypes and the ratios you would expect to see for each phenotype in the F2 generation. Since white is located on the X chromosome, you should keep your male and female phenotypic classes separate.

Answer 1

Explanation:

a.

- Genotypes of the parental generation:

- Male: X^wY (hemizygous for white)

- Female: X^WX^W (true breeding, wild-type)

b.

- Expected genotypes and phenotypes in the F1 generation:

- All offspring will be X^wX^W females (heterozygous for white) with wild-type phenotype.

c.

- Punnett square for the genotypes expected in the F2 progeny:

- **Females:** X^WX^W, X^wX^W

- **Males:** X^WY, X^wY

d.

- Phenotypes and ratios in the F2 generation:

- **Females:**

- Wild-type (red-eyed): X^WX^W (50%)

- White-eyed: X^wX^W (50%)

- **Males:**

- Wild-type (red-eyed): X^WY (50%)

- White-eyed: X^wY (50%)

The expected phenotypes in the F2 generation would show a 1:1 ratio for white-eyed and red-eyed individuals in both males and females due to the inheritance pattern of the white gene located on the X chromosome.