The points at which crossing over has taken place between homologous chromosomes are called

Options

A. Protein axis
B. Synaptonemal complexes
C. Chiasmata
D. Centromeres

Answer

To solve the question, we need to identify the correct term that describes the points at which crossing over occurs between homologous chromosomes. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Crossing Over
Crossing over is a process that occurs during meiosis, where homologous chromosomes exchange genetic material. This leads to genetic variation in the resulting gametes.

**Hint:** Remember that crossing over is a key event in meiosis that increases genetic diversity.

### Step 2: Identify the Options
The question provides several options. We need to analyze each one to determine which one correctly describes the points of crossing over.

**Hint:** Look for terms specifically related to chromosome structure and behavior during meiosis.

### Step 3: Analyze Each Option
1. **Protein Axis**: This term refers to the structural framework of proteins and is unrelated to chromosomes or crossing over.

**Hint:** Consider whether the term relates to chromosomes or genetic processes.

2. **Synaptonemal Complex**: This is a structure that forms during prophase I of meiosis, where homologous chromosomes become closely associated. However, it does not specifically refer to the points of crossing over.

**Hint:** This term is related to the pairing of chromosomes but does not denote the specific crossing points.

3. **Chiasmata**: This is the correct term. Chiasmata are the physical points where homologous chromosomes cross over and exchange genetic material. They appear as X-shaped structures during metaphase.

**Hint:** Think about the visual representation of crossing over and how it relates to the structure of chromosomes.

4. **Centromere**: This is the region of a chromosome where the two sister chromatids are joined. It does not relate to crossing over.

**Hint:** Remember that the centromere is involved in chromosome movement during cell division but is not related to genetic exchange.

### Step 4: Conclusion
Based on the analysis, the correct answer is **Chiasmata**. This is the term that describes the points at which crossing over occurs between homologous chromosomes.

**Final Answer:** Chiasmata