Bivalents first appear during

Options

A. Leptotene
B. Zygotene
C. Pachytene
D. Diplotene

Answer

**Step-by-Step Solution:**

1. **Understanding Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four haploid daughter cells from one diploid cell. It consists of two main stages: Meiosis I and Meiosis II.

2. **Prophase I of Meiosis**: The first stage of Meiosis I is Prophase I, which is further divided into five sub-stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

3. **Identifying the Sub-stages**:
- **Leptotene**: Chromosomes begin to condense and become visible under a light microscope.
- **Zygotene**: Homologous chromosomes begin to pair up in a process called synapsis, forming bivalents.
- **Pachytene**: Bivalents are fully formed, and crossing over (recombination) occurs.
- **Diplotene**: The homologous chromosomes start to separate but remain connected at points called chiasmata.
- **Diakinesis**: The chromosomes condense further and prepare for metaphase.

4. **Bivalents Appearance**: Bivalents, which consist of a pair of homologous chromosomes, first appear during the Zygotene stage due to the process of synapsis.

5. **Conclusion**: Based on the information above, the correct answer to the question "Bivalents first appear during" is Zygotene.

**Final Answer**: Zygotene

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