Number of base pairs present in DNA wrapped around a core of histone proteins

Options

A. 146
B. 154
C. 200
D. 54

Answer

To determine the number of base pairs present in DNA wrapped around a core of histone proteins, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Nucleosomes**:
- Nucleosomes are the fundamental units of chromatin, consisting of a segment of DNA wrapped around a core of histone proteins. Each nucleosome contains a core made up of histone proteins (H2A, H2B, H3, and H4).

2. **Identify the Core Histone Composition**:
- The core histone proteins consist of two copies each of H2A, H2B, H3, and H4. This forms the histone octamer around which the DNA is wrapped.

3. **Determine the Amount of DNA Wrapped**:
- The DNA wraps around the histone core in a specific manner. In one nucleosome, the DNA makes approximately 1.67 turns around the histone proteins.

4. **Calculate the Base Pairs per Turn**:
- It is established that approximately 146 base pairs of DNA are wrapped around the histone core in one complete nucleosome.

5. **Conclude the Total Base Pairs**:
- Therefore, the number of base pairs present in the DNA wrapped around a core of histone proteins in one nucleosome is 146 base pairs.

### Final Answer:
The number of base pairs present in DNA wrapped around a core of histone proteins is **146 base pairs**.

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