Genetic pedigree analysis worksheet key with three family trees illustrating inheritance patterns for Huntington's Disease, Hitchhiker's Thumb, and colorblindness.

Let’s go step by step through each question on the worksheet. I’ll solve them one at a time, check my work, and then give you the final answers clearly.

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Question 1: Which members of the family above are afflicted with Huntington’s Disease?

Looking at the pedigree (first chart), filled-in shapes = affected.

- Generation II: II-2 (female, filled circle), II-3 (male, filled square), II-7 (female, filled circle)
- Generation III: III-3 (female, filled circle)

Wait — also look at generation I: I-1 is filled square → affected.

So list all:

I-1
II-2, II-3, II-7
III-3

That’s 5 people.

But wait — let me double-check the image description in the user’s upload. The key says black/filled = Huntington’s. In the first pedigree:

Row I: male (square) filled → I-1 affected
Row II: females II-2 and II-7 filled; male II-3 filled → so 3 in row II
Row III: female III-3 filled → 1 in row III

Total: I-1, II-2, II-3, II-7, III-3 → 5 individuals

✔ Confirmed.

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Question 2: There are no carriers for Huntington’s Disease – you either have it or you don’t. With this in mind, is Huntington’s disease caused by a dominant or recessive trait?

If there are NO carriers, that means if you have even one copy of the gene, you show the disease → that’s dominant.

Also, looking at the pedigree: I-1 has it, passes to some kids but not all → consistent with dominant (not every child gets it).

And unaffected parents (like II-4 and II-5) have only unaffected kids → makes sense for dominant (if they didn’t inherit the allele, they can’t pass it).

✔ Answer: Dominant

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Question 3: How many children did individuals I-1 and I-2 have?

Look at generation II under I-1 and I-2.

They have lines going down to: II-1, II-2, II-3, II-4, II-5, II-6, II-7, II-8 → that’s 8 children.

Count: 1,2,3,4,5,6,7,8 → yes, 8.

✔ Answer: 8

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Question 4: How many girls did II-1 and II-2 have? How many have Huntington’s Disease?

II-1 (male, unfilled) and II-2 (female, filled) → their children are in generation III: III-1 (boy), III-2 (girl), III-3 (girl)

So girls: III-2 and III-3 → 2 girls

Which have Huntington’s? III-3 is filled → affected. III-2 is unfilled → not affected.

So only 1 girl has it.

✔ Answers: 2 girls, 1 has Huntington’s

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Question 5: How are individuals III-2 and II-4 related? Uncle/Niece? Grandson/Granddaughter?

III-2 is daughter of II-1 and II-2.

II-4 is brother of II-2 (same parents: I-1 and I-2).

So II-4 is uncle of III-2.

Therefore: Uncle and Niece

Now second part: “II-2 and III-5?”

III-5 is son of II-4 and II-5.

II-2 is sister of II-4 → so II-2 is aunt of III-5.

But the question says “II-2 and III-5” → that would be Aunt and Nephew.

Wait — the original question says: “How are individuals III-2 and II-4 related? ... II-2 and III-5?”

Actually, re-reading: “How are individuals III-2 and II-4 related? Uncle/Niece II-2 and III-5? Grandma/Grandson”

Hmm — maybe typo? Let’s parse:

It probably means:

Part A: III-2 and II-4 → as above, Uncle/Niece

Part B: II-2 and III-5 → II-2 is aunt of III-5 → so Aunt/Nephew

But the answer choices given are “Uncle/Niece” and “Grandma/Grandson”

Wait — perhaps it's asking two separate relationships:

First: III-2 and II-4 → Uncle/Niece ✔

Second: Who is related how between II-2 and III-5? But III-5 is child of II-4, who is sibling of II-2 → so II-2 is aunt → not grandma.

Unless... maybe misread generations?

No — III-5 is generation III, II-2 is generation II → cannot be grandma.

Perhaps the question meant: “How are individuals III-2 and II-4 related? [Answer: Uncle/Niece]” and separately “How are II-2 and III-5 related?” but the text says “II-2 and III-5? Grandma/Grandson” — which doesn't fit.

Wait — maybe it's a formatting issue. Looking back at user input:

“5. How are individuals III-2 and II-4 related? Uncle/Niece II-2 and III-5? Grandma/Grandson”

Ah — perhaps it's two questions mashed together:

Q5a: III-2 and II-4 → Uncle/Niece

Q5b: II-2 and III-5 → ? But III-5 is nephew of II-2 → not grandson.

Unless... is III-5 child of someone else? No — III-5 is child of II-4 and II-5.

Another possibility: Maybe “II-2 and III-5” is