Which of these pairs is correctly matched ?

Options

A. Female heterogamety - Humans
B. 2n + 1 of sex chromosome - Turner's syndrome
C. 2n + 1 of sex chromosomes - Trisomy
D. Pleiotropic gene - Gene for phenylketonuria

Answer

To solve the question "Which of these pairs is correctly matched?", we will analyze each option provided and determine if the pair is correctly matched based on biological concepts.

### Step-by-Step Solution:

1. **Analyze the First Option:**
- **Pair:** Female heterogamy - Humans
- **Explanation:** In humans, males have XY chromosomes (heterogametic), while females have XX chromosomes (homogametic). Therefore, this option is incorrect because humans exhibit male heterogamy, not female.

**Hint:** Remember that in humans, males are the heterogametic sex due to the presence of X and Y chromosomes.

2. **Analyze the Second Option:**
- **Pair:** 2N + 1 of sex chromosome - Turner's syndrome
- **Explanation:** Turner's syndrome is characterized by the presence of only one X chromosome (45,X), which means it does not have an extra chromosome. This option is also incorrect as it suggests an additional chromosome.

**Hint:** Turner's syndrome involves a missing chromosome, not an extra one.

3. **Analyze the Third Option:**
- **Pair:** 2N + 1 of sex chromosome - Trisomy
- **Explanation:** Trisomy refers to the presence of an extra chromosome, which can occur in various conditions (e.g., Down syndrome, Klinefelter syndrome). The notation 2N + 1 indicates that there is one extra chromosome, making this option correct.

**Hint:** Trisomy is defined by having one more chromosome than the typical diploid number.

4. **Analyze the Fourth Option:**
- **Pair:** Pleiotropic gene - Phenylketonuria (PKU)
- **Explanation:** Pleiotropy refers to a single gene affecting multiple traits. While PKU is caused by a single gene mutation, it does not exemplify the concept of pleiotropy in the context of this question. Therefore, this option is incorrect.

**Hint:** Pleiotropic genes influence multiple traits, but PKU is primarily a metabolic disorder.

### Conclusion:
After analyzing all the options, the only correctly matched pair is the third option: **2N + 1 of sex chromosome - Trisomy**.

### Final Answer:
The correct answer is the third option.