Final answer:
DNA in eukaryotic cells is compactly packed by wrapping around histone proteins to form nucleosomes and further condensing into a 30 nm fiber, eventually forming chromosomes for cell division. This complex packing allows the 2-meter-long DNA to fit within the microscopic nucleus of a cell.
Step-by-step explanation:
Packing DNA into the Cell Nucleus
The process of efficiently fitting the long molecules of DNA inside the relatively small cell nucleus is intricate and involves multiple levels of organization. Eukaryotic cells achieve this by wrapping DNA around proteins known as histones to form structures called nucleosomes. The nucleosomes, together with DNA, organize into a formation reminiscent of "beads on a string" and are further compacted into a thicker 30 nm fiber. As a cell prepares to divide during mitosis, this arrangement condenses even more drastically, eventually forming what we identify as chromosomes, ensuring that DNA is neatly packaged and protected for cell division.
The 2-meter-long human cell DNA is tightly bound around these histone beads and then coiled into structures that lead to a remarkable degree of compaction. Furthermore, the entire structure undergoes successive levels of folding and looping, which eventually determine the distinctive X-shaped structure of chromosomes observable under a microscope during the metaphase of cell division. These highly coiled structures feature centromeres and chromatin fibers, which play crucial roles in the accurate distribution of genetic material to daughter cells.