BIOL 2520 Lecture Notes - Lecture 6: H2Afy, Xist (Gene), Barr Body
1 Dec 2016
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Document Summary
Storing dna is an exercise in organization: the human genome: Is written in 6 x 108 nucleotide bases. Is divided into 46 chromosomes, each an unbroken strand. Is a total of 2m long in the nucleus of 10 um in diameter. Dna winds around nucleosomes, which are composed of a group of positively charged, highly conserved proteins- histones: histones form a core of eight proteins that make a nucleosome, dna negatively charged because of phosphates in backbone. Dna is held by the histones due to non-covalent bonds, especially ionic bonds between negatively charged phosphate backbone of dna and positive charge of histones. Nucleosomes: made up of four histones, two of each: Dna wraps around the nucleosomes 1. 8 turns or 146 nucleotide bases per nucleosome. Histone h1 (fifth type)- the linker histone. Sits outside the nucleosome, and helps compact to the point of a very small fiber of dna as well. A total of 168 nucleotide bases per unit.
