A bivalent of meiosis i consists of

Options

A. two chromatids and one centromere
B. two chromatids and two centromeres
C. four chromatids and two centromeres
D. four chromatids and four centromeres.

Explanation

To answer the question "A bivalent of meiosis I consists of," we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Bivalent Formation**:
- During meiosis I, specifically in the prophase I stage, bivalents are formed during a sub-stage called zygotene.

2. **Composition of a Bivalent**:
- A bivalent consists of two homologous chromosomes. Each of these chromosomes is made up of two sister chromatids.

3. **Counting Chromatids**:
- Since there are two homologous chromosomes and each chromosome has two sister chromatids, we can calculate the total number of chromatids:
- 2 homologous chromosomes × 2 sister chromatids each = 4 chromatids.

4. **Counting Centromeres**:
- Each chromosome has one centromere. Therefore, with two homologous chromosomes, the total number of centromeres is:
- 2 homologous chromosomes = 2 centromeres.

5. **Final Composition of Bivalent**:
- Thus, a bivalent in meiosis I consists of:
- 4 chromatids and 2 centromeres.

### Conclusion:
A bivalent of meiosis I consists of **4 chromatids and 2 centromeres**.

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