Number of DNA molecules in a metaphase chromosome is

Options

A. Many
B. Three
C. One
D. Two

Answer

To determine the number of DNA molecules in a metaphase chromosome, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Chromosomes**:
- During metaphase, chromosomes are highly condensed and visible under a microscope. Each chromosome consists of two identical halves called sister chromatids.

2. **Identify the Phase of the Cell Cycle**:
- The question specifies "metaphase," which is a stage in mitosis where chromosomes align at the metaphase plate.

3. **Recall DNA Replication**:
- Prior to metaphase, during the S phase of the cell cycle, DNA replication occurs. This means that each chromosome is replicated, resulting in two sister chromatids.

4. **Count the DNA Molecules**:
- Each sister chromatid contains one molecule of double-stranded DNA. Since there are two sister chromatids in a metaphase chromosome, we have:
- 1 DNA molecule in the first sister chromatid
- 1 DNA molecule in the second sister chromatid
- Therefore, in total, there are 2 DNA molecules in a metaphase chromosome.

5. **Conclude the Answer**:
- The number of DNA molecules in a metaphase chromosome is **2**.

### Final Answer:
The number of DNA molecules in a metaphase chromosome is **2**.

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