Which among the following histone proteins is least conserved in course of evolution?

Options

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

Answer

To determine which histone protein is least conserved during evolution, we need to analyze the different types of histones and their conservation levels.

### Step-by-Step Solution:

1. **Understand Histone Proteins**: Histones are proteins that help package DNA into a compact, organized structure called chromatin. There are five main types of histones: H1, H2A, H2B, H3, and H4.

2. **Identify Nucleosome Structure**: A nucleosome consists of a core of histone proteins around which DNA is wrapped. The core is made up of two copies each of H2A, H2B, H3, and H4, while H1 is a linker histone that connects nucleosomes.

3. **Conservation of Histones**: Histones are generally highly conserved across species, which means their sequences have remained relatively unchanged throughout evolution. However, some histones are more variable than others.

4. **Focus on H1 Histone**: Among the histones, H1 is known to be the least conserved. It shows significant variation in its sequence across different species. This variability is due to its role as a linker histone, which can adapt to different chromatin structures and functions.

5. **Conclusion**: Based on the analysis, the histone protein that is least conserved in the course of evolution is H1.

### Final Answer:
The least conserved histone protein in the course of evolution is **H1** (Option D).

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