OCR A Biology
Dna Wound Histones Addition Tightly Makes Cell Chromatin
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Transcriptional control - Chromatin remodelling |
| Back |
- DNA wound around histones (as opp charged, DNA -ve and histones +ve) forming chromatin complex so DNA compact enough to fit in nucleus
- acetylation (addition of acetyl group)/phosphorylation (addition of phosphate group) make histines more -ve so DNA less tightly wound, so now certain genes can be transcribed, forms Euchromatin (loosley wound DNA present in interphase) which makes gene accessible (transcription can occur)
- methylation (addition of methyl group) makes histones more hydrophobic so they bind more tightly to eachother, and DNA more tightly wound so no transcription, forms Heterochromatin (tightly wound DNA that causes chromosomes to be visable during cell division) and makes genes inaccessible for RNA polymerase (so no transcription)
- these 2 known as epigenetics (control of gene expression by modification of DNA)
- protein synthesis happens during interphase, and this regulation ensures proteins for cell division formed and prevents protein synthesis during cell division
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OCR A Biology