Final answer:
The nucleosomal core contains DNA wrapped around an octamer of histones, forming a 'bead-like' structure that is part of the 'beads on a string' arrangement in chromatin. This structure facilitates the compaction of DNA within the nucleus and becomes even more compact during metaphase.
Step-by-step explanation:
The Nucleosomal Core
The nucleosomal core consists of a complex of DNA wrapped around a group of proteins known as histones. These histones form an octamer, featuring two copies each of H2A, H2B, H3, and H4, creating a bead-like structure. About 146 base pairs of DNA wind around this histone core, with a linker DNA segment spanning adjacent nucleosomes. This configuration is often referred to as the "beads on a string" structure. Additionally, a fifth histone, H1, plays a role in further compacting the string of nucleosomes into a 30 nm fiber. During the metaphase of mitosis, chromosomes reach their most compact form, where nucleosomes associate with scaffold proteins to form a structure approximately 700 nm in width.