human there are 23 bivalents in metaphase -I, what will be the number of chromosomes in daughter cells after meiosis - I and meiosis - II?

Options

A. 46 and 46
B. 92 and 46
C. 23 and 23
D. 46 and 23

Answer

To solve the problem regarding the number of chromosomes in daughter cells after meiosis I and meiosis II, follow these steps:

### Step-by-Step Solution:

1. **Understanding Bivalents**:
- In metaphase I of meiosis, bivalents are formed. Each bivalent consists of two homologous chromosomes.
- Given that there are 23 bivalents, we can deduce that there are 23 pairs of homologous chromosomes.

2. **Calculating Total Chromosomes**:
- Since each bivalent consists of 2 chromosomes, the total number of chromosomes can be calculated as:
\[ \text{Total Chromosomes} = \text{Number of Bivalents} \times 2 = 23 \times 2 = 46 \]
- Therefore, there are 46 chromosomes in total before meiosis begins.

3. **Meiosis I**:
- During meiosis I, the homologous chromosomes are separated into different daughter cells. This reduces the chromosome number by half.
- Thus, after meiosis I, the number of chromosomes in each daughter cell will be:
\[ \text{Chromosomes after Meiosis I} = \frac{46}{2} = 23 \]

4. **Meiosis II**:
- Meiosis II is similar to mitosis, where the sister chromatids of each chromosome are separated. However, the number of chromosomes remains the same since we are separating the sister chromatids.
- Therefore, after meiosis II, the number of chromosomes in each daughter cell will still be:
\[ \text{Chromosomes after Meiosis II} = 23 \]

5. **Final Answer**:
- The number of chromosomes in daughter cells after meiosis I is 23, and after meiosis II, it remains 23.

### Summary:
- After meiosis I: **23 chromosomes**
- After meiosis II: **23 chromosomes**