GEN-3000 Lecture Notes - Lecture 11: Supercooling, Chromatin, Euchromatin
Document Summary
E. coli genome is 4. 6 map about 1000x longer than cell. Human cell= 6. 5 ft of dna inside the nucleus. Dna structure has three levels to consider: primary structure-nucleotide sequence, secondary structure-double stranded helix, tertiary structure-higher order packing. Most dna is negatively supercool with the help of topoisomerases. Separation of stands is easier, occupies less space than relaxed. Bacterial dna is packed with proteins not histones. Along with other proteins to interact with dna. Chromatin: complex of dna and proteins in eurkaryotic chromosomes. 1/2 of protein mass=non-histone chromosomal proteins (scaffolding proteins and dna replication/maintenance proteins/transcription proteins) Heterochromatin: highly condensed chromatin-silent dna not actively using. Euchromatin: chromatin can be transcriptionally active-in use (open chromatin-available) Scaffold proteins (non histone): play role is folding/packing dna. 4 histones- 2 copies of each=8 + dna. Chromatin remodeling: structure must change to allow access to dna. Methylation: shutting down of dna (not always true) Undergone repeated rounds of replication with out cellular division.
