What are nucleosomes composed of?

Nucleosomes are the fundamental units of chromatin and are essential for packaging DNA within the nucleus of eukaryotic cells. Each nucleosome consists of a segment of DNA, typically around 146 base pairs long, that is wrapped around a core of eight histone proteins. This structure allows for efficient organization and compaction of DNA, fitting it into the limited space of the cell's nucleus.

The eight histone proteins come together to form a histone octamer, which consists of two molecules each of histones H2A, H2B, H3, and H4. This tightly packed structure not only protects the DNA but also plays a crucial role in regulating gene expression and DNA replication processes.

The other options do not accurately describe the composition of nucleosomes. While nucleic acids, such as RNA, and other DNA structures exist in cells, nucleosomes specifically refer to the combination of DNA and histone proteins that organize eukaryotic chromatin. The correct understanding of nucleosomes is fundamental for grasping concepts related to DNA structure, function, and gene regulation.