An abnormal human male phenotype involving an extra Y-chromosome (XYY) is a case of

Options

A. Edward's syndrome
B. Jacob syndrome
C. Intersex
D. Down's syndrome

Answer

To solve the question regarding the abnormal human male phenotype involving an extra Y-chromosome (XYY), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Chromosomal Abnormality**:
- The question specifies an abnormal human male phenotype with an extra Y chromosome, which can be represented as XYY.

2. **Identifying the Syndrome**:
- The presence of an extra Y chromosome in males is associated with a specific genetic condition. This condition is known as Jacob's syndrome.

3. **Characteristics of Jacob's Syndrome**:
- Males with Jacob's syndrome typically exhibit certain physical traits, such as being taller than average. This syndrome is a result of the presence of an additional Y chromosome.

4. **Differentiating from Other Syndromes**:
- It's important to distinguish Jacob's syndrome from other genetic disorders:
- **Edwards Syndrome**: Involves trisomy of chromosome 18 (not related to the Y chromosome).
- **Intersex Conditions**: May involve variations in sex chromosomes, but not specifically XYY.
- **Down Syndrome**: Involves trisomy of chromosome 21 (again, not related to the Y chromosome).

5. **Conclusion**:
- Based on the information gathered, the correct answer to the question is Jacob's syndrome, which corresponds to option B.

### Final Answer:
The abnormal human male phenotype involving an extra Y-chromosome (XYY) is a case of **Jacob's syndrome**.

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