Sex-Linked Pedigrees Worksheet illustrating the inheritance of hemophilia through a family tree with genotypes and phenotypes.

Let’s go step by step to solve this pedigree problem about hemophilia, which is a recessive sex-linked disorder on the X chromosome.

We’re told:
- Squares = males
- Circles = females
- Shaded = has the disorder (hemophilia)
- Unshaded = does not have the disorder
- Genotypes are written below each person
- For phenotype questions: first line = male or female; second line = normal, carrier, or hemophilia

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Step 1: Understand the genotypes and what they mean

Hemophilia is recessive and X-linked. So:

- Males have one X and one Y → if their X has the bad allele (X^h), they have hemophilia. If it’s X^H, they’re normal.
- Females have two X chromosomes:
- X^H X^H → normal (not carrier)
- X^H X^h → carrier (doesn’t have disease but can pass it on)
- X^h X^h → has hemophilia (rare, since needs two bad alleles)

In this pedigree, we see that shaded individuals are those with hemophilia — so any male with X^h Y is shaded, and any female with X^h X^h would be shaded (but in this chart, no female is shaded, meaning no female has hemophilia — only carriers or normals).

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Step 2: Look at each question one by one

#### Question 2: Phenotype of individual 2?

Individual 2 is a circle → female

Genotype given: X^H X^h → she has one good allele and one bad allele → carrier

✔ Answer: Female, carrier

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#### Question 3: Phenotype of individual 4?

Individual 4 is a square → male

Genotype: X^h Y → he has the bad allele on his only X → has hemophilia

Also, he’s shaded → confirms he has the disorder.

✔ Answer: Male, hemophilia

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#### Question 4: Phenotype of individual 5?

Individual 5 is a square → male

Genotype: X^h Y → same as above → has hemophilia

He’s also shaded → confirms.

✔ Answer: Male, hemophilia

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#### Question 5: Phenotype of individual 7?

Individual 7 is a square → male

Genotype: X^H Y → he has the good allele → normal

Not shaded → matches.

✔ Answer: Male, normal

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#### Question 6: Phenotype of individual 9?

Individual 9 is a circle → female

Genotype: X^H X^h → one good, one bad → carrier

Not shaded → correct, because carriers don’t show the disease.

✔ Answer: Female, carrier

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#### Question 7: Phenotype of individual 10?

Individual 10 is a square → male

Genotype: X^H Y → good allele → normal

Not shaded → correct.

✔ Answer: Male, normal

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All answers match the genotypes provided and the rules of X-linked recessive inheritance.

Final Answer:
2) Female, carrier
3) Male, hemophilia
4) Male, hemophilia
5) Male, normal
6) Female, carrier
7) Male, normal