Pedigrees Worksheet for Genetics | Made By Teachers - Free Printable

Pedigree Analysis: Solving the Problems

The provided image shows a pedigree chart and several questions related to it. Below is a detailed explanation of each question and its solution.

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#### Pedigree Chart Recap
- Symbols:
- Square: Male
- Circle: Female
- Shaded: Affected individual
- Unshaded: Unaffected individual
- Marriage line: Connecting two individuals who are married
- Key Observations:
- Generation I (I-1 and I-2) are both affected.
- Generation II has some affected and unaffected individuals.
- Generation III has more affected individuals.
- Generation IV has one unaffected individual so far.

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Questions and Solutions

#### 1. How many generations are in this pedigree?
- Solution: Count the rows in the pedigree chart.
- There are 4 rows labeled as I, II, III, and IV.
- Answer: 4 generations

#### 2. How many marriages are in this pedigree?
- Solution: Count the marriage lines connecting individuals.
- Generation I: 1 marriage (I-1 and I-2)
- Generation II: 3 marriages (II-1 and II-2, II-3 and II-4, II-5 and II-6)
- Total: 1 + 3 = 4 marriages
- Answer: 4 marriages

#### 3. How many individuals are affected?
- Solution: Count all shaded symbols (affected individuals).
- Generation I: 2 (I-1 and I-2)
- Generation II: 2 (II-2 and II-5)
- Generation III: 3 (III-1, III-2, and III-4)
- Generation IV: 0
- Total: 2 + 2 + 3 + 0 = 7
- Answer: 7 individuals

#### 4. What is the sex of II-4?
- Solution: Look at the symbol for II-4.
- II-4 is represented by a square, which denotes a male.
- Answer: Male

#### 5. How many children did couple I-1 and I-2 have?
- Solution: Count the number of offspring from the marriage of I-1 and I-2.
- I-1 and I-2 have 4 children: II-1, II-2, II-3, and II-4.
- Answer: 4 children

#### 6. Who did II-2 marry?
- Solution: Identify the spouse of II-2 by looking at the marriage line.
- II-2 is connected to II-1 by a marriage line.
- Answer: II-1

#### 7. What is the genotype of individual II-2?
- Solution: Determine the genotype of II-2 based on the pedigree information.
- II-2 is shaded, indicating they are affected.
- The disorder appears to be autosomal recessive because:
- Both parents (I-1 and I-2) are affected (dd).
- Some offspring are unaffected (e.g., II-3 and II-4), which is consistent with autosomal recessive inheritance.
- Since II-2 is affected, their genotype must be dd.
- Answer: dd

#### 8. What is the genotype of individual II-5?
- Solution: Determine the genotype of II-5 based on the pedigree information.
- II-5 is shaded, indicating they are affected.
- Similar to II-2, the disorder is autosomal recessive.
- Therefore, II-5's genotype must also be dd.
- Answer: dd

#### 9. What is the genotype of individual III-3?
- Solution: Determine the genotype of III-3 based on the pedigree information.
- III-3 is unshaded, indicating they are unaffected.
- Their parents (II-3 and II-4) are both carriers (Dd) because:
- II-3 and II-4 are unaffected but have an affected sibling (II-2 or II-5).
- Since III-3 is unaffected, their genotype must be DD or Dd.
- However, since we don't have additional information about III-3's offspring, we can only conclude that they are at least a carrier (Dd).
- Answer: Dd

#### 10. What is the genotype of individual IV-1?
- Solution: Determine the genotype of IV-1 based on the pedigree information.
- IV-1 is unshaded, indicating they are unaffected.
- Their parents (III-3 and III-4) are both carriers (Dd).
- Since IV-1 is unaffected, their genotype must be DD or Dd.
- However, since we don't have additional information about IV-1's siblings or offspring, we can only conclude that they are at least a carrier (Dd).
- Answer: Dd

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Final Answers

1. 4 generations
2. 4 marriages
3. 7 individuals
4. Male
5. 4 children
6. II-1
7. dd
8. dd
9. Dd
10. Dd

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Shading Instructions

- All affected individuals (shaded symbols) should already be shaded in the pedigree chart. No additional shading is needed based on the given information.

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Final Boxed Answers

\[
\boxed{
\begin{array}{l}
1. \text{4 generations} \\
2. \text{4 marriages} \\
3. \text{7 individuals} \\
4. \text{Male} \\
5. \text{4 children} \\
6. \text{II-1} \\
7. \text{dd} \\
8. \text{dd} \\
9. \text{Dd} \\
10. \text{Dd}
\end{array}
}
\]