Final answer:
DNA has a negative charge which allows it to associate with positively charged histone proteins, forming the nucleosome, a fundamental unit of chromatin structure in eukaryotes.
Step-by-step explanation:
In a nucleosome, DNA can associate with histone proteins because DNA has a negative charge and the histone proteins have a positive charge. This attraction is due to the acidic and negatively charged phosphodiester backbone of DNA and the basic nature of histones, which contain positively charged amino acids, primarily lysine and arginine. This interaction allows the DNA to wrap around an octamer of histones, forming the nucleosome.
Furthermore, histones are highly conserved proteins crucial for DNA packing inside the nucleus. They help organize the DNA into a 10 nm filament known as the "beads-on-a-string" structure, which further folds into a 30 nm fiber. During the metaphase stage of cell division, this structure is even more condensed to fit within the nucleus.