In Zygotene, homologous chromosomes undergo pairing to form bivalent having 2 homologous chomosomes. These 2 chromosomes are attached larerally due to

Options

A. U protein
B. centromere
C. Ribonucleoprotein
D. Endonuclease

Answer

To solve the question regarding the attachment of homologous chromosomes during the zygotene stage of meiosis, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Zygotene**: In the zygotene stage of meiosis, homologous chromosomes begin to pair up. This process is known as synapsis, where each chromosome aligns with its homologous partner.

2. **Formation of Bivalents**: The paired homologous chromosomes are referred to as bivalents. Each bivalent consists of two homologous chromosomes, which are closely aligned along their lengths.

3. **Lateral Attachment**: The two homologous chromosomes in a bivalent are attached laterally. This attachment is crucial for the proper segregation of chromosomes during meiosis.

4. **Identifying the Mechanism of Attachment**: The attachment of homologous chromosomes laterally in the bivalent is primarily due to a protein structure known as the **synaptonemal complex**. However, in the context of the options provided in the question, we need to identify the correct term.

5. **Evaluating the Options**:
- **A. Euprotein**: This is not a recognized term in this context.
- **B. Sendromia**: This term is likely a misinterpretation or misspelling of "syndesmos" or "synapsis," which refers to the lateral attachment of homologous chromosomes.
- **C. Ribonucleoprotein**: This refers to complexes of RNA and protein but does not specifically relate to chromosome pairing.
- **D. Endonuclease**: This is an enzyme that cuts DNA but is not involved in the attachment of homologous chromosomes.

6. **Conclusion**: Based on the understanding of the zygotene stage and the options provided, the correct answer is **B. Sendromia**, which is interpreted as the mechanism that allows for the lateral attachment of homologous chromosomes.

### Final Answer:
The two homologous chromosomes are attached laterally due to **Sendromia**.

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