Number of bivalents are 8 in prophase I. What is the number of chromosomes during anaphase II ?

Options

A. 8
B. 4
C. 16
D. 32

Answer

To solve the question regarding the number of chromosomes during anaphase II when the number of bivalents is 8 in prophase I, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Bivalents**:
- A bivalent is a pair of homologous chromosomes that come together during prophase I of meiosis. Each bivalent consists of two chromosomes.

2. **Calculate the Total Number of Chromosomes in Prophase I**:
- Given that there are 8 bivalents, we can calculate the total number of chromosomes:
\[ \text{Total Chromosomes} = \text{Number of Bivalents} \times 2 = 8 \times 2 = 16 \]
- Therefore, there are 16 chromosomes in prophase I.

3. **Identify the Chromosome Number at the End of Meiosis I**:
- Meiosis I is a reductional division, meaning it reduces the chromosome number by half.
- Since we started with 16 chromosomes (2n), after meiosis I, the number of chromosomes will be:
\[ \text{Chromosomes after Meiosis I} = \frac{16}{2} = 8 \]

4. **Determine the Number of Chromosomes in Anaphase II**:
- Anaphase II occurs after meiosis I has already taken place. The chromosome number remains the same during meiosis II until anaphase II, where sister chromatids are separated.
- Therefore, the number of chromosomes during anaphase II will still be 8.

### Final Answer:
The number of chromosomes during anaphase II is **8**.

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