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|Chapter Six: DNA, RNA, and Protein Synthesis|
If you were to take one molecule of DNA from a human cell and stretch it out to its full length, it would be approximately two meters long. So it is truly incredible that such an enormously long molecule can be compressed into the microscopic space of the nucleus of a cell.
We will start from the very beginning of the packaging: the actual DNA molecule. It is first wrapped twice around a cluster of protein molecules called histones. This structure, a cluster of histones and two loops of DNA around it, is called a nucleosome. But this packing is not nearly enough to squeeze the tremendous DNA molecule into the nucleus. The nucleosomes are subsequently coiled together, and then this coil is arranged in tightly packed loops. This incredibly dense mass of loops and coils is the condensed chromatin that you would see in the nucleus of a cell.