BIOL308 Lecture 5: Lecture 5
11 Jun 2017
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Document Summary
Primary structure of dna =double helix = 2 nm duplexdna. Duplex dna winds around histone octamers to form nucleosomes= 10-11 nm histone fiber. Nucleosome fibers condense into 30 nm chromatin fiber. Different theories regarding its form (solenoid or zig-zag form). 30 nm chromatin fiber condenses (over successive steps) to a metaphase chromosome = 400nm attachment of chromatin fibers to nonhistone protein complexes or scaffold/matrix (most genes are inscaffold loops) Looped domains encompass most of the genes in the 30nm fibers. There are a lot of studies being carried out to try and understand how things are divided up in the nucleus. Compartmentalized distribution of functional components in the nucleus. Euchromatin: loose or open structure, transcriptionally active dna, susceptible to dnase i digestion. Trans factor can get in and bind to sequence. Heterochromatin: dense or closed structure, transcriptionally inactive, susceptible to dnase i digestion.
