What is a nucleosome composed of?

A nucleosome is fundamentally composed of DNA wrapped around a histone octamer. This structure serves as the basic unit of DNA packaging in eukaryotic cells, facilitating the efficient organization of DNA within the cell nucleus.

The histone octamer consists of eight histone proteins—two copies each of H2A, H2B, H3, and H4. The DNA molecule, typically around 147 base pairs long, wraps approximately 1.65 times around this octamer, creating a compact and organized structure that is crucial for DNA condensation during cell division. Moreover, this arrangement plays a significant role in regulating gene expression and DNA replication, as the accessibility of the genetic material can be modulated by the configuration and interaction of the nucleosome with other proteins and factors.

In contrast, other options such as DNA wrapped around mRNA, DNA bound to linker proteins, or nucleotides linked in a chain do not accurately describe the composition of a nucleosome. Option A mischaracterizes the nature of nucleic acids involved; option C touches upon the structural elements in chromatin but does not represent the core structure of the nucleosome, which is specifically the interaction of DNA with histones. Lastly, option D describes the basic building