Worksheet on sex-linked inheritance in fruit flies, illustrating eye color genetics with red and white eye traits.

You've uploaded a worksheet titled “Practice Problems: Sex Linked Genes” focused on eye color inheritance in fruit flies, where:

- Eye color is sex-linked (on the X chromosome).
- Red (Xᴿ) is dominant to white (Xʳ).
- Males are XY, females are XX.

Let’s go through each question and verify/correct the answers with clear explanations.

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✔ Question 1: What are the sexes and eye colors of flies with the following genotypes?

You filled in:
- XᴿXʳ → red female ✔️
*(Heterozygous female — dominant red allele expressed)*
- XᴿY → red male ✔️
*(Male has only one X — if it’s Xᴿ, he has red eyes)*
- XʳXʳ → white female ✔️
*(Homozygous recessive — white eyes)*
- XᴿXᴿ → red female ✔️
*(Homozygous dominant — red eyes)*
- XʳY → white male ✔️
*(Male with recessive Xʳ — white eyes)*

✔ All correct!

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✔ Question 2: What are the genotypes of these flies?

You filled in:
- white eyed, male → XʳY ✔️
*(Only possible genotype for white-eyed male)*
- red eyed female (heterozygous) → XᴿXʳ ✔️
*(Heterozygous = one dominant, one recessive)*
- white eyed, female → XʳXʳ ✔️
*(Females need two recessive alleles to show white eyes)*
- red eyed, male → XᴿY ✔️
*(Males express whatever allele is on their single X)*

✔ All correct!

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✔ Question 3: Cross between white-eyed female (XʳXʳ) and red-eyed male (XᴿY)

Parental Genotypes:
- Female: XʳXʳ
- Male: XᴿY

Gametes:
- Female → all eggs: Xʳ
- Male → sperm: Xᴿ or Y (50% each)

Offspring:

| Egg \ Sperm | Xᴿ | Y |
|-------------|----------|----------|
| Xʳ | XᴿXʳ | XʳY |

→ Females: All XᴿXʳ → red-eyed (since Xᴿ is dominant)
→ Males: All XʳY → white-eyed

So:

- white eyed, male → 50% ✔️
- white eyed, female → 0% ✘ *(You wrote 0% — actually correct!)*
- red eyed, male → 0% ✔️
- red eyed, female → 50% ✔️

✔ Your answer is correct!

*(Note: You wrote “0%” for white-eyed female — that’s right. Females get Xᴿ from dad → red eyes.)*

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✔ Question 4: Cross between pure red-eyed female and white-eyed male

Pure red-eyed female = homozygous dominant → XᴿXᴿ
White-eyed male = XʳY

Gametes:
- Female → all Xᴿ
- Male → Xʳ or Y

Offspring:

| Egg \ Sperm | Xʳ | Y |
|-------------|----------|----------|
| Xᴿ | XᴿXʳ | XᴿY |

→ Females: XᴿXʳ → red-eyed
→ Males: XᴿY → red-eyed

So:

- white eyed, male → 0% ✔️
- white eyed, female → 0% ✔️
- red eyed, male → 50% ✔️
- red eyed, female → 50% ✔️

✔ All correct!

*(Note: You wrote “XᴿXᴿ and XʳY” for parents — perfect!)*

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✔ Question 5: Cross between red-eyed female (heterozygous) and red-eyed male

Female (heterozygous): XᴿXʳ
Male: XᴿY

Gametes:
- Female → Xᴿ or Xʳ (50% each)
- Male → Xᴿ or Y (50% each)

Punnett Square:

| Egg \ Sperm | Xᴿ | Y |
|-------------|----------|----------|
| Xᴿ | XᴿXᴿ | XᴿY |
| Xʳ | XᴿXʳ | XʳY |

Offspring:

- XᴿXᴿ → red-eyed female (25%)
- XᴿXʳ → red-eyed female (25%) → total 50% red-eyed females
- XᴿY → red-eyed male (25%)
- XʳY → white-eyed male (25%)

So:

- white eyed, male → 25% ✔️
- white eyed, female → 0% ✔️
- red eyed, male → 25% ✔️
- red eyed, female → 50% ✔️

✔ All correct!

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🧮 Math Problem: If 100 males and 200 females were produced, how many total red-eyed flies?

From the cross above (Q5):

- Males: 50% red-eyed (XᴿY), 50% white-eyed (XʳY)
→ 100 males × 50% = 50 red-eyed males

- Females: ALL red-eyed (XᴿXᴿ or XᴿXʳ)
→ 200 females × 100% = 200 red-eyed females

✔ Total red-eyed flies = 50 + 200 = 250

You wrote “250” — ✔️ Correct!

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## 🎯 Final Summary:

✔ All your answers are CORRECT!

This worksheet demonstrates classic X-linked inheritance:

- Males express whichever allele is on their single X.
- Females need two recessive alleles to show the recessive trait.
- In crosses, you can predict phenotypic ratios using Punnett squares based on sex chromosomes.

Great job! 👏

If you want to visualize any of the Punnett squares or need help with more problems, feel free to ask!