The two nucleosomes are joined by linker DNA to which is attached

Options

A. `H_(1)`
B. `H_(2)`
C. `H_(3)`
D. `H_(4)`

Answer

To solve the question regarding what is attached to the linker DNA that joins two nucleosomes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Nucleosomes**:
- Nucleosomes are the fundamental units of chromatin, consisting of a segment of DNA wrapped around a core of histone proteins. Each nucleosome is often described as "beads on a string."

2. **Composition of Nucleosomes**:
- Each nucleosome consists of a core made up of eight histone proteins: two copies each of H2A, H2B, H3, and H4. This forms the histone octamer.

3. **Linker DNA**:
- The DNA that connects two nucleosomes is referred to as linker DNA. This linker DNA is not tightly bound to the histone core and serves to connect adjacent nucleosomes.

4. **Role of H1 Histone**:
- The linker DNA is associated with a specific histone known as H1. H1 histone binds to the linker DNA and helps in the compaction of the chromatin structure by stabilizing the nucleosome arrangement.

5. **Identifying the Correct Answer**:
- Given the options (H1, H2, H3, H4), the histone that is specifically associated with linker DNA is H1. Therefore, the correct answer to the question is H1.

### Final Answer:
The two nucleosomes are joined by linker DNA to which is attached **H1**.

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