Final answer:
Histones are proteins around which DNA wraps to form nucleosomes, which then coil into chromatin and further condense into chromosomes during cell division. The chromatin's condensation level varies, with euchromatin being less packed and heterochromatin being more compact.
Step-by-step explanation:
In eukaryotic cells, DNA is wrapped around proteins called histones to form structures known as nucleosomes. These nucleosomes are linked together by linker DNA, resembling 'beads on a string'. As the DNA folds and coils further, it forms a 30-nm chromatin fiber. During cell division, this chromatin can condense into tightly packed chromosomes, ensuring the DNA is transported swiftly to daughter cells. Histones are crucial in this process as they are rich in basic amino acids, forming an octamer around which the DNA tightly coils.
Chromatin exists in two forms within the cell—euchromatin, which is less compact and usually contains active genes being transcribed, and heterochromatin, which is more densely packed and contains genes that are typically not expressed. The most condensed form of DNA during the cell cycle occurs in metaphase, where chromosomes are tightly packed with scaffold proteins, measuring approximately 700 nm in width.