Detailed educational worksheet on sex-linked traits, covering genetic inheritance patterns and including practice problems with a Punnett square for fruit fly eye color.

Final Answer:
1. X
2. Male
3. One
4. Two
5. Males have only one X chromosome, so if it carries the colorblind allele, they show the trait. Females have two X chromosomes, so they need both to carry the allele to be colorblind — otherwise, the normal allele on the other X can mask it.
6. A “carrier” is a person (usually female) who has one copy of the abnormal gene for an X-linked trait but does not show symptoms because they also have a normal gene on their other X chromosome.

──────────────────────────────────────

Explanation:
Let’s go through each question one by one — like we’re walking through it together.

1. X-linked traits are inherited on the X chromosome. That’s why they’re called “X-linked.” Simple!

2. Males are more likely to have X-linked traits. Why? Because males have only one X chromosome (and one Y). If that one X has a bad gene, they don’t have another X to fix it. Females have two Xs, so even if one has a bad gene, the other might be good and hide the problem.

3. Males have one X chromosome. Their sex chromosomes are XY — so just one X.

4. Females have two X chromosomes. Their sex chromosomes are XX — so two Xs.

5. Colorblindness is X-linked recessive. Males only have one X — so if that X has the colorblind gene, they’re colorblind. Females have two Xs — so they’d need both Xs to have the bad gene to be colorblind. If only one has it, they’re usually just carriers and see colors normally.

6. A “carrier” is someone (usually a female) who has one bad gene for an X-linked trait but doesn’t show the disease because her other X chromosome has the normal gene. She can pass the bad gene to her kids, though.

Now let’s do the fruit fly problem:

We’re told:
- White eyes = recessive, sex-linked → gene symbol: r
- Red eyes = dominant → gene symbol: R
- Female is white-eyed → so her genotype must be XʳXʳ (because she needs two copies to show the recessive trait)
- Male is red-eyed → his genotype is XᴿY (males only have one X, so if he has red eyes, his X must have the R gene)

Now we make a Punnett square:

The female gives either Xʳ or Xʳ (both the same).
The male gives either Xᴿ or Y.

So offspring:

- Females: all get Xᴿ from dad and Xʳ from mom → XᴿXʳ → red eyes (because R is dominant)
- Males: all get Xʳ from mom and Y from dad → XʳY → white eyes (because they only have one X, and it’s the recessive one)

So:

a. Percent of males with red eyes? 0%
Percent of males with white eyes? 100%

b. Percent of females with red eyes? 100%
Percent of females with white eyes? 0%

c. Total percent of offspring that are white-eyed? Only the males are white-eyed. Since half the offspring are males, that’s 50%.

And that’s it! You got this. 😊