Meiosis and mitosis are found to be the tow types of cell division . A cell is observed to have 50 chromosomes in its nucleus during interphase before entering S-phase . How many chromosomes will it have after undergoing division by the two - division process ?
`{:(,"Meiosis","Mitosis"),(1,100,25),(2,50,50),(3,50,100),(4,25,50):}`

Options

A. 1
B. 2
C. 3
D. 4

Answer

To solve the question, we need to analyze the process of cell division, specifically focusing on meiosis and mitosis, and how they affect the number of chromosomes in a cell.

### Step-by-Step Solution:

1. **Understanding the Initial Condition**:
- We start with a cell that has 50 chromosomes during interphase (specifically in the G1 phase).

2. **Entering the S Phase**:
- When the cell enters the S phase, DNA replication occurs. This means that each chromosome is duplicated.
- After the S phase, the number of chromosomes is still counted as 50, but each chromosome now consists of two sister chromatids. So, we still have 50 chromosomes, but they are now replicated.

3. **Mitosis**:
- Mitosis is a type of cell division that results in two daughter cells, each with the same number of chromosomes as the original cell.
- Since our original cell has 50 chromosomes, after mitosis, each daughter cell will also have 50 chromosomes.

4. **Meiosis**:
- Meiosis consists of two rounds of division: Meiosis I and Meiosis II.
- In Meiosis I, the homologous chromosomes are separated, resulting in two cells, each with half the number of chromosomes (haploid).
- Since we started with 50 chromosomes, after Meiosis I, we will have two cells, each with 25 chromosomes.
- In Meiosis II, the sister chromatids are separated, resulting in a total of four daughter cells. Each of these cells will also have 25 chromosomes.

5. **Final Count of Chromosomes**:
- After mitosis, we have 2 daughter cells with 50 chromosomes each.
- After meiosis, we have 4 daughter cells with 25 chromosomes each.

### Conclusion:
- The answer to the question is:
- After mitosis: 50 chromosomes in each of the 2 daughter cells.
- After meiosis: 25 chromosomes in each of the 4 daughter cells.

### Answer Options:
- Mitosis: 50 chromosomes (in each daughter cell)
- Meiosis: 25 chromosomes (in each daughter cell)

Thus, the correct answer is option 4: (25, 50).