BIOMG 1350 Chapter Notes - Chapter 5,8 : Cytosine, Heterochromatin, Histone Deacetylase
9 Nov 2016
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Document Summary
Changes in nucleosome structure allow access to dna: chromatin-remodeling complexes. Protein machines that use the energy of atp hydrolysis to change the position of dna wrapped around nucleosomes. Attach to both histone octamer and dna wrapped around it. During mitosis inactivated: chemical modification of histones. On the tails of all four of core histones (covalent modifications) Acetyl, phosphate, methyl groups can be added or removed. Acetylation of lysine reduces affinity of tails for nucleosomes. Loosens chromatin structure: modifications can serve as docking site on histone tails. Promote decondensation: facilitate access to dna, histone modifying enzymes work in concert with chromatin-remodeling complexes to decondense/condense stretches of chromatin. Interphase chromosomes contain both condensed and more extended forms of. Chromatin: most cells express about 20-30% of genes they contain, heterochromatin. Most dna in heterochromatin does not contain genes. Genes accidently packaged failed to be expressed can cause: euchromatin disease silenced genes.
