Which of the following is correct?

Options

A. DNA replication occur before mitosis but not meiosis.
B. In human cells, chromosome are visible only during mitosis and meiosis.
C. During meiosis centromere divides in anaphase I.
D. Crossing overtakes place in meiosis II.

Answer

To determine which of the statements regarding the cell cycle and cell division is correct, we can analyze the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding DNA Replication**:
- DNA replication occurs during the S phase of interphase. This is a crucial step that happens before both mitosis and meiosis. Therefore, the statement that "DNA replication occurs before mitosis but not in meiosis" is incorrect.

2. **Chromosome Visibility**:
- Chromosomes are only visible during the M phase of the cell cycle, which includes both mitosis and meiosis. During interphase (G1, S, and G2 phases), the genetic material exists in a less condensed form known as chromatin. Thus, the statement "in human cells chromosomes are visible only during mitosis and meiosis" is correct.

3. **Interphase Definition**:
- Interphase consists of three phases: G1 (Gap 1), S (Synthesis), and G2 (Gap 2). During this time, the cell prepares for division, and DNA is replicated in the S phase.

4. **M Phase**:
- The M phase is where the actual division occurs, and it includes both mitosis and meiosis. During this phase, the chromatin condenses to form visible chromosomes.

5. **Conclusion**:
- Based on the analysis, the correct statement is that chromosomes are visible only during mitosis and meiosis.

### Final Answer:
The correct statement is: "In human cells, chromosomes are visible only during mitosis and meiosis."