Overview Composition DNA - charge histone proteins + charge from Lys and Arg residues H2A, H2B, H3, H4 (core proteins) H1 (linking protein) post-translational modification of histone tails forms a code interpreted by effector proteins to regulate transcription downstream histone acetyltransferase (HAT) acetyl group added which blocks positive charge of histone protein and loosens interaction with DNA ↑ transcription histone deacetylase (HDAC) removes acetyl group which exposes positive charge and tightens interactions ↓ transcription electrostatic attraction of DNA with histone proteins Organization 10 nm chromatin DNA wraps around dimer of H2A:H2B:H3:H4 called nucleosome sensitive to nuclease activity 30 nm chromatin nucleosomes held together by H1 not sensitive to nuclease activity 30 nm fiber loops further condensation Euchromatin/heterochromatin euchromatin = accessible to transcription 10 nm through 30 nm fiber loops heterochromatin = not accessible to transcription any greater condensation than 30 nm fiber loops condensed to save room
QUESTIONS 1 of 2 1 2 Previous Next (M1.BC.17.4708) A 62-year-old man with small cell lung cancer undergoes radiation therapy. His oncologist explains that radiation causes DNA damage and double-strand breaks, and this damage stops the cancer cells from growing because they can no longer replicate their DNA. One key mediator of this process is a cell cycle regulator called P53, which is upregulated after DNA damage and helps to trigger cell cycle arrest and apoptosis. One mechanism by which P53 activity is increased is a certain chromatin modification that loosens DNA coiling allowing for greater transcription of the proteins within that region of DNA. Which of the following enzymes most likely causes the chromatin modification described in this case? QID: 108463 Type & Select Correct Answer 1 DNA methyltransferase 12% (20/173) 2 Histone acetyltransferase 59% (102/173) 3 Histone deacetylase 17% (30/173) 4 DNA topoisomerase 10% (18/173) 5 Xist 1% (1/173) M 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
All Videos (1) Login to View Community Videos Login to View Community Videos Chromatin and DNA regulation Biochemistry - Chromatin Structure D 2/14/2015 238 views 4.9 (8) Biochemistry | Chromatin Structure Biochemistry - Chromatin Structure Listen Now 10:19 min 3 weeks ago 2 plays 0.0 (0)