BIOB11H3 Lecture Notes - Lecture 7: Histone H1, Heterochromatin, Satellite Dna
Document Summary
2m of dna into a nucleus that is 10 m in diameter. Nucleosomes lowest level of organization, discovered by. Dna + histone (8 histones 2 x h2a, 2 x h2b, 2 x h3, 2 x h4) Dna wound around 1. 8 times (around 200 bp), gets 7x more compact. Histone h1 + core nucleosome = 30 nm fiber increasing packaging ratio 6-fold, so it is now 40-fold. Nucleosomes form a double helix as they are lined up in 2 stack ends to end. Maintenance of fiber depends on interactions b/w histone mc of neighbouring nucleosomes. Packed about 6 nucleosomes per turn with h1 facing inside of solenoid structure. Chromatin not being actively transcribed present in 30 nm fibers or looped domains. 30 nm fiber can be seen under em at physiological [salt] conditions. If the [salt] is too high, the core histones denature. Loops attach to nuclear proteins that are part of the nuclear matrix.
