A bivalent is:

Options

A. two daughter cells after meiosis
B. a duplicated chromosome composed of sister chromatids
C. paired homologous chromosomes
D. a homologous chromosome

Answer

To answer the question "A bivalent is:", we will analyze the options provided and determine the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding the Term "Bivalent":**
- A bivalent refers to a structure that forms during meiosis, specifically during the prophase I stage.

2. **Identifying the Stages of Meiosis:**
- Meiosis consists of two main stages: Meiosis I and Meiosis II.
- Prophase I of Meiosis I is further divided into several stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.

3. **Focus on the Zygotene Stage:**
- The formation of bivalents occurs during the zygotene stage of prophase I.
- During this stage, homologous chromosomes (chromosomes that are similar in shape, size, and genetic content) come together and pair up.

4. **Definition of Bivalent:**
- A bivalent is defined as a pair of homologous chromosomes that are aligned together. Each homologous chromosome consists of two sister chromatids, but the term "bivalent" specifically refers to the pairing of the two homologous chromosomes.

5. **Evaluating the Options:**
- Option A: Two daughter cells after meiosis - This is incorrect as a bivalent is not a daughter cell.
- Option B: A duplicated chromosome composed of sister chromatids - This is incorrect as it refers to a single chromosome, not a pair.
- Option C: Paired homologous chromosomes - This is correct as it accurately describes a bivalent.
- Option D: A homologous chromosome - This is incorrect as it refers to only one chromosome, not the paired structure.

6. **Conclusion:**
- Based on the analysis, the correct answer is **C: paired homologous chromosomes**.