Question

1. what are the genotypes of these flies:

white eyed, male _____________ red eyed female (heterozygous) _______
white eyed, female _____________ red eyed, male _____________

1. show the cross of a white eyed female $x^{r}x^{r}$ with a red-eyed male $x^{r}y$.

how many are:
white eyed, male ____
white eyed, female ____
red eyed, male ____
red eyed, female ____

Explanation:

Step1: Define eye color alleles

Eye color in fruit flies is X-linked: $X^R$ = red (dominant), $X^r$ = white (recessive). Males have XY, females have XX.

Step2: Solve Question 2 genotypes

Substep2a: White-eyed male

Males get 1 X allele. White eyes need $X^r$, so genotype is $X^rY$.

Substep2b: White-eyed female

Females need 2 recessive alleles: $X^rX^r$.

Substep2c: Heterozygous red-eyed female

One dominant, one recessive allele: $X^RX^r$.

Substep2d: Red-eyed male

Males get dominant X allele: $X^RY$.

Step3: Set up Punnett Square (Question3)

Parent 1 (white-eyed female): $X^rX^r$ (gametes: $X^r$, $X^r$)
Parent 2 (red-eyed male): $X^RY$ (gametes: $X^R$, $Y$)
Fill Punnett Square:

	$X^R$	$Y$
$X^r$	$X^RX^r$	$X^rY$

Step4: Count offspring phenotypes (Question3)

Substep4a: White-eyed male

2 out of 4 offspring: $\frac{2}{4} = 50\%$ or 2 (if counting total 4)

Substep4b: White-eyed female

0 out of 4 offspring: 0

Substep4c: Red-eyed male

0 out of 4 offspring: 0

Substep4d: Red-eyed female

2 out of 4 offspring: $\frac{2}{4} = 50\%$ or 2 (if counting total 4)

Answer:

Question 2 Genotypes:

white eyed, male: $X^rY$
white eyed, female: $X^rX^r$
red eyed female (heterozygous): $X^RX^r$
red eyed, male: $X^RY$

Question 3 Punnett Square & Counts:

Punnett Square:

	$X^R$	$Y$
$X^r$	$X^RX^r$	$X^rY$

Offspring Counts:

white eyed, male: 2 (50%)
white eyed, female: 0
red eyed, male: 0
red eyed, female: 2 (50%)