True about nucleosome: (PGI Nov 2009)
**Core Concept**
A nucleosome is a basic unit of chromatin in eukaryotic cells, consisting of a segment of DNA wound around a core of histone proteins. The nucleosome plays a crucial role in DNA packaging and gene regulation by controlling the accessibility of DNA to transcription factors and other regulatory proteins.
**Why the Correct Answer is Right**
The correct answer is related to the structure of the nucleosome. The nucleosome core consists of eight histone proteins (two copies each of histones H2A, H2B, H3, and H4), around which a segment of DNA is wrapped. This wrapping of DNA around the histone core is stabilized by a combination of electrostatic and hydrophobic interactions. The correct answer is likely related to this structural aspect of nucleosomes.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically describe a structural feature of nucleosomes.
**Option B:** This option is incorrect because it refers to a different aspect of chromatin structure, such as the linker DNA, which is not directly related to the nucleosome core.
**Option C:** This option is incorrect because it describes a process or function of nucleosomes, rather than a structural feature.
**Clinical Pearl / High-Yield Fact**
Nucleosomes play a critical role in regulating gene expression by controlling the accessibility of DNA to transcription factors. Abnormal nucleosome dynamics have been implicated in various diseases, including cancer and autoimmune disorders.
**Correct Answer:** C.