Final answer:
DNA in eukaryotic cells is organized into chromosomes and is wrapped around positively charged histone proteins to form nucleosome structures. This results in a "beads on a string" format, which is further compacted into a 30 nm fiber and highly condensed during metaphase. Epigenetic factors can influence this packaging, altering gene expression without modifying the DNA sequence.
Step-by-step explanation:
In eukaryotic cells, DNA is organized into chromosomes where it is intricately packed to fit within the nucleus. At the most basic level of this organization, DNA is wound around histone proteins to form nucleosomes. Histones are positively charged due to their rich content of basic amino acids, which allows them to interact with the negatively charged phosphate groups in the DNA.
These nucleosomes are likened to "beads on a string", with each bead representing a nucleosome and the string representing DNA. Further compaction occurs when the nucleosomes are packed tightly together to form a 30 nm fiber. During the metaphase stage of cell division, chromosomes achieve the highest level of compaction, at about 700 nm in width, involving additional scaffolding proteins that help maintain the structure.
Epigenetic factors can modulate the histone-DNA interaction, thereby influencing gene expression without altering the underlying DNA sequence, which demonstrates the dynamic nature of chromosome packaging in eukaryotes.