Knight/Chromatin Structure and DNA Packing/2001 Chromatin Structure and DNA Packing “Oh What a Tangled Web We Weave- Sir Walter Scott. 1771-1832!” DNA packing is required since the nucleus of an eukaryotic cell is so small (5 – 8 µm) and the length of DNA in the nucleus is about 2 meters! (This is equivalent to a tennis ball with 12 miles of thread stuffed in it!)DNA is packaged and folded using proteins, coiling and looping to increase the organization of the DNA and prevent it from being unmanageable and a tangled mess. Each chromosome consists of a single, very long piece of DNA that is associated with proteins (histones) that is folded and packed into a more compact structure. DNA is bound to the histones (5 sub-types make up a functioning histone) through electrostatic forces between the negatively charged phosphate groups in the DNA backbone and positively charged amino acids in the histone proteins. The DNA winds around the proteins (1.8 turns per histone or about 200 b.p.)
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