Pedigree analysis worksheet illustrating genetic inheritance of Huntington's disease, Hitchhiker's thumb, and colorblindness across generations.

Problem Analysis and Solution

The document provided contains several pedigree analysis questions related to genetic traits. Below, I will solve each problem step by step with detailed explanations.

---

#### Part 1: Huntington's Disease Pedigree

##### Question 1
- How many children did individuals I-1 and I-2 have?
- From the pedigree, we can see that individuals I-1 and I-2 have 6 children (II-1, II-2, II-3, II-4, II-5, II-6, II-7, II-8).
- Answer: 6

- How many HAVE Huntington’s Disease?
- Individuals with Huntington’s Disease are represented by black symbols.
- In this pedigree, individuals II-2, II-3, and II-7 have Huntington’s Disease.
- Answer: 3

##### Question 2
- How many daughters did II-1 and II-2 have?
- II-1 and II-2 have 2 daughters (III-2 and III-3).
- Answer: 2

- How many sons did II-1 and II-2 have?
- II-1 and II-2 have 1 son (III-1).
- Answer: 1

##### Question 3
- How are individuals III-2 and II-4 related?
- III-2 is the daughter of II-1 and II-2.
- II-4 is the son of I-1 and I-2.
- Therefore, III-2 is the niece of II-4.
- Answer: Uncle/Niece

- How are individuals II-2 and III-5 related?
- II-2 is the mother of III-5.
- Answer: Grandmother/Grandson

##### Question 4
- Is Huntington’s disease caused by a dominant or recessive trait?
- The question states that there are no carriers for Huntington’s Disease; you either have it or you don’t.
- This indicates that the disease is caused by a dominant allele.
- Answer: Dominant

##### Question 5
- Write the genotypes over all known individuals. Represent unknowns with question marks.
- I-1: Hh (affected)
- I-2: hh (unaffected)
- II-1: hh (unaffected)
- II-2: Hh (affected)
- II-3: Hh (affected)
- II-4: hh (unaffected)
- II-5: hh (unaffected)
- II-6: hh (unaffected)
- II-7: Hh (affected)
- II-8: hh (unaffected)
- III-1: hh (unaffected)
- III-2: hh (unaffected)
- III-3: Hh (affected)
- III-4: hh (unaffected)
- III-5: hh (unaffected)

---

#### Part 2: Hitchhiker’s Thumb Pedigree

##### Question 6
- Is this trait dominant or recessive?
- The trait is shown in individual IV-1, but neither parent (III-1 and III-2) has the trait.
- For a recessive trait, both parents must be carriers (heterozygous) to produce an affected offspring.
- Answer: Recessive

##### Question 7
- How do you know?
- If the trait were dominant, at least one parent (III-1 or III-2) would need to have the trait.
- Since neither parent has the trait, the trait must be recessive.
- Answer: If it was dominant, either Parent III-1 or III-2 would have the trait.

##### Question 8
- Write the genotypes of above individuals with Hitchhiker’s Thumbs (use T / t).
- IV-1 has the trait (tt).
- III-1 and III-2 are carriers (Tt).
- II-2 and II-3 are carriers (Tt).
- II-5 and II-6 are carriers (Tt).
- I-2 and I-4 are carriers (Tt).

##### Question 9
- How are individuals III-1 and III-2 related?
- III-1 and III-2 are cousins and married.
- Answer: Cousins AND married

##### Question 10
- Write the genotypes above individuals III-1 and III-2.
- III-1: Tt
- III-2: Tt

##### Question 11
- Is it possible for individual IV-2 to be a carrier? Why or why not?
- Yes, it is possible for IV-2 to be a carrier.
- Both parents (III-1 and III-2) are heterozygous (Tt), so they can pass on the recessive allele (t) to their offspring.
- Answer: Yes, parents are heterozygous

---

#### Part 3: Colorblindness Pedigree

##### Question 12
- Which sex can be carriers of colorblindness and not have it?
- Females can be carriers of colorblindness (X^NXⁿ) and not express the trait because they have one normal allele (X^N).
- Males cannot be carriers; they either have the trait (XⁿY) or do not have it (X^NY).
- Answer: Females

##### Question 13
- What kind of trait is colorblindness?
- Colorblindness is a sex-linked recessive trait because it is located on the X chromosome and is expressed only when two copies of the recessive allele are present in females or one copy in males.
- Answer: Sex linked and recessive

##### Question 14
- Write the genotypes above all individuals.
- I-1: XⁿY (affected)
- I-2: X^NX^N (unaffected)
- II-1: X^NY (unaffected)
- II-2: X^NXⁿ (carrier)
- II-3: X^NY (unaffected)
- II-4: X^NX^N (unaffected)
- II-5: X^NY (unaffected)
- II-6: X^NXⁿ (carrier)
- III-1: X^NY (unaffected)
- III-2: X^NXⁿ (carrier)
- III-3: XⁿY (affected)
- III-4: X^NX^N (unaffected)
- III-5: X^NY (unaffected)
- III-6: X^NXⁿ (carrier)
- III-7: XⁿY (affected)
- III-8: X^NY (unaffected)
- IV-1: XⁿY (affected)
- IV-2: X^NX^N (unaffected)
- IV-3: X^NXⁿ (carrier)
- IV-4: X^NX^N (unaffected)
- IV-5: XⁿY (affected)
- IV-6: X^NXⁿ (carrier)
- IV-7: XⁿY (affected)
- IV-8: X^NY (unaffected)

##### Question 15
- Why do all daughters in generation II carry the colorblind gene?
- All daughters in generation II received a colorblind allele (Xⁿ) from their father (I-1), who is affected (XⁿY).
- Answer: They received a colorblind allele from dad.

##### Question 16
- If individual IV-7 had children, what percentage of her sons would you expect to be colorblind?
- IV-7 is affected (XⁿY), so she will pass the Xⁿ allele to all her sons.
- Therefore, 100% of her sons will be colorblind.
- Answer: 100%

---

Final Answers:

1. 6 children, 3 have Huntington’s Disease
2. 2 daughters, 1 son
3. Uncle/Niece, Grandmother/Grandson
4. Dominant
5. Genotypes as explained above
6. Recessive
7. If it was dominant, either Parent III-1 or III-2 would have the trait
8. Genotypes as explained above
9. Cousins AND married
10. III-1: Tt, III-2: Tt
11. Yes, parents are heterozygous
12. Females
13. Sex linked and recessive
14. Genotypes as explained above
15. They received a colorblind allele from dad
16. 100%

Final Answer: \boxed{100\%}