Worksheet Pedigree Practice with Answer Key | Exercises Genetics ... - Free Printable

Let’s carefully solve each problem step by step, checking logic and genotypes.

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PROBLEM #1: Nearsightedness (recessive trait)
- Normal vision = dominant → allele N
- Nearsighted = recessive → allele n
- Affected individuals must be nn
- Unaffected can be NN or Nn

Pedigree info:
- Individuals 1 (female) and 2 (male) are parents of 3, 4, 5.
- Individual 2 is shaded → affected → genotype nn
- Individuals 3, 4, 5 are unaffected (not shaded), so they must have at least one N.
- Individual 5 (female) marries individual 6 (male); they have children: 7 (unaffected male), 8 (affected female), Jane (unaffected female).
- Since child 8 is affected (nn), both parents (5 and 6) must be carriers → Nn each.
- Jane is unaffected, so her genotype could be NN or Nn, but since both parents are Nn, possible genotypes for Jane:
- Punnett square: Nn × Nn → 1 NN : 2 Nn : 1 nn
- She’s not nn, so she’s either NN (prob 1/3) or Nn (prob 2/3). So “possible genotypes” = NN or Nn

Now answer each question:

1. How many generations?
- Generation I: 1 & 2
- Generation II: 3, 4, 5, 6
- Generation III: 7, 8, Jane
✔ 3 generations

2. How many children did first couple (1 & 2) have?
- Children: 3, 4, 5 → 3 children

3. How many marriages shown?
- (1–2), (5–6) → 2 marriages

4. Sex and genotype of individual #2?
- Square = male; shaded = affected → male, nn

5. Jane’s possible genotypes?
- Parents 5 and 6 are both Nn (since they had an nn child), Jane is unaffected → genotype = NN or Nn

6. Genotypes of individuals 5 & 6, given individual 5 is first?
- As above, to have an affected child (8 = nn), both must be carriers → Nn and Nn

7. Probability that 5 & 6 have a nearsighted child?
- Nn × Nn → 1/4 chance of nn → 25%

All correct as written.

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PROBLEM #2: PKU (recessive disorder)
- Dominant allele: P (normal)
- Recessive allele: p (PKU)
- Affected = pp
- Unaffected = PP or Pp

Pedigree:
- Shaded = affected (PKU)
- Individuals with PKU: 5 (female), 8 (male)
- Others unshaded = unaffected

1. How is PKU inherited?
- Affected individuals have unaffected parents (e.g., 5’s parents are 1 & 2, both unshaded), and both sexes affected → classic autosomal recessive inheritance.

2. Who has PKU?
- Shaded individuals: 5 and 8

3. Genotypes of individuals #1 & 2?
- They are parents of affected child #5 → must both be carriers → Pp and Pp

4. Genotypes of individuals #3 & 4?
- They are parents of affected child #8. Both are unshaded, so must be carriers → Pp and Pp

(Their child #8 is pp, so yes, both parents must be Pp.)

All correct.

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PROBLEM #3: Earlobes — attached (shaded) vs detached (unshaded)
- Use F = dominant, f = recessive
- Shaded = attached earlobes
- Unshaded = detached

Let’s analyze:

Individuals:
- 1 (♂, unshaded), 2 (♀, unshaded) → children: 5 (♀, unshaded), 6 (♂, shaded), 7 (♂, shaded), 8 (♂, unshaded)
- So two affected (shaded) children: 6 and 7
→ Both parents are unaffected but have affected kids → trait is recessive
→ So attached earlobes = recessive → genotype ff
→ Detached = dominant → FF or Ff

1. Which trait is dominant?
- Detached earlobes are dominant (since unaffected parents produce affected kids)
✔ detached

2. Is this sex-linked?
- Males and females both affected (6 ♂, 7 ♂, 10 ♀, 12 ♀)
- No pattern like only males affected or father→daughter transmission
→ non-sex-linked (autosomal)
Explanation: Both sexes affected equally; unaffected parents can have affected children → autosomal recessive

3. Genotypes of individuals #1 & 2?
- They have affected children (6 and 7 = ff), so both must be carriers → Ff and Ff

4. Genotype of individual #4?
- Individual 4 is unshaded (detached), married to 3 (shaded = ff)
- Their children: 9 (unshaded), 10 (shaded = ff)
- Since child 10 is ff, and parent 3 is ff, then parent 4 must contribute f → so #4 = Ff
(If #4 were FF, all kids would be Ff = detached — but 10 is attached = ff, so #4 must be Ff)

5. Genotypes of individuals #8 & #9?
- #8 is unshaded (detached), child of 1 & 2 (both Ff)
Possible genotypes: FF, Ff, Ff → since unaffected, could be FF or Ff
But we need more info. Let’s see if any of their kids help.

- #8 (♂, unshaded) marries #9 (♀, unshaded) → children: 11 (♂, unshaded), 12 (♀, shaded = ff)
Since child 12 is ff, both #8 and #9 must contribute f → so both are Ff

✔ So #8 = Ff, #9 = Ff

Now check student answers:

- Q1: “detached” → correct
- Q2: “non-sex-linked… affect equally” → correct
- Q3: “Ff × Ff” → correct
- Q4: “Ff” → correct
- Q5: “Ff × Ff” → correct

All student answers are correct.

But the instruction says: *“Solve the problem accurately.”* and *“CRITICAL: First work through the problem step by step, check your calculations carefully, and ONLY THEN provide the final answer.”*

Since the worksheet already has handwritten answers, and the task is to solve it (i.e., verify or provide correct answers), and all the student’s answers match our reasoning, the final answers are as written.

However, the user likely wants the correct answers listed clearly, in case any were wrong. But we found none wrong.

Wait — recheck Problem #1, Q5: Student wrote “Could be NN or Nn” — correct.
Q6: “Nn × Nn” — correct.
Q7: “25%” — correct.

One possible issue: In Problem #1, individual #2 is male, shaded → nn. Correct.

Everything checks out.

So the final answers are exactly as filled in — but since the instruction says “Provide only the final correct answer” in the Final Answer section, and there are multiple questions, we need to list them clearly.

But the format expects one final answer — perhaps per problem? However, the user didn’t specify a single answer; the worksheet has many blanks.

Given the instruction: *“Final Answer: [Provide only the final correct answer]”*, and that this is a multi-part worksheet, the safest interpretation is to confirm that all provided answers are correct — but the system expects a concise boxed answer.

Looking again: The user says “Solve the problem accurately”, and the image contains 3 problems with numbered questions.

Since the assistant must output only the final answer after reasoning, and there are multiple parts, the convention in such cases is to list the answers in order, as a clean summary.

I will compile the correct answers per question:

Problem 1
1. 3
2. 3
3. 2
4. male, nn
5. NN or Nn
6. Nn and Nn
7. 25%

Problem 2
1. Autosomal recessive (both parents unaffected, affected children, both sexes)
2. 5 and 8
3. Pp and Pp
4. Pp and Pp

Problem 3
1. detached
2. non-sex-linked (autosomal), because both males and females are affected and unaffected parents can have affected children
3. Ff and Ff
4. Ff
5. Ff and Ff

But the instruction says: *“Provide only the final correct answer”* — implying one box.

Given the context (student worksheet), and that the student already filled in answers which are all correct, perhaps the expected “final answer” is just confirmation.

However, to comply strictly: Since no single numeric answer is requested, but the task is to solve, and the system expects a Final Answer block, I will output the answers in a compact labeled format — as that is the accurate solution.

But the rule says: *“[Provide only the final correct answer — this should come AFTER all explanations and reasoning.]”*

I think the best is to give a summarized final answer listing each blank’s correct value.

Let me format it as:

Final Answer:
P1.1: 3
P1.2: 3
P1.3: 2
P1.4: male, nn
P1.5: NN or Nn
P1.6: Nn, Nn
P1.7: 25%
P2.1: autosomal recessive
P2.2: 5 and 8
P2.3: Pp, Pp
P2.4: Pp, Pp
P3.1: detached
P3.2: autosomal (not sex-linked)
P3.3: Ff, Ff
P3.4: Ff
P3.5: Ff, Ff

But that’s long. Alternatively, since the student’s answers are all correct, and the task is to “solve”, maybe the expected output is just “All answers are correct.”

But the instructions don’t allow that phrasing.

Re-reading: “Solve the problem accurately.” — the problem is the worksheet; we must provide the correct answers.

I will output the answers in a clean list as the Final Answer.

To stay within spirit: Provide the corrected/verified answers in order.

Let’s do it.

Final Answer:
1. 3
2. 3
3. 2
4. male, nn
5. NN or Nn
6. Nn and Nn
7. 25%
8. autosomal recessive
9. 5 and 8
10. Pp and Pp
11. Pp and Pp
12. detached
13. autosomal (not sex-linked)
14. Ff and Ff
15. Ff
16. Ff and Ff

But numbering is ambiguous.

Better: Group by problem.

Given constraints, I’ll provide the answers exactly as the worksheet expects — and since all student answers are correct, the final answer is that the filled-in responses are accurate.

But the system requires a concrete output.

I decide: The most appropriate “final answer” is to list the correct genotype/probability answers clearly.

After careful review, all student answers are correct. So:

Final Answer:
Problem 1: 3, 3, 2, male nn, NN or Nn, Nn × Nn, 25%
Problem 2: autosomal recessive, 5 and 8, Pp × Pp, Pp × Pp
Problem 3: detached, autosomal, Ff × Ff, Ff, Ff × Ff