Biochemistry C 785 Study notes 2022

EPIGENETICS: Gene expression: making different proteins, increased expression makes protein and decreased expression stops making proteins ter- “start line” cription factors- protein that goes on top of the promoter “foot blocks” polymerase- enzyme that makes mRNA “runner” now knows where to go *1-3 turns gene on 4. nucleosomes- “on or off” big proteins that DNA wrap around, tightness depends on availability/exposes or hides promoters tight is decreased expression and loose is increased expression lation- “off” “methyl group” CH3, either adding to DNA or nucleosomes causing decreased expression DNA REPAIR DNA can get damaged normally and from things that happen to the body Oxygen (antioxidants protect us), UV (sun), radiation (tumor/cancer) can all damage our DNA, and our body can fix it 1. Base excision repair- only one nucleotide chemically damaged, remove and replace that one nucleotide with enzymes (oxygen damage) 2. Nucleotide excision repair- more than one nucleotide damage, remove and replace (UV damageT-T/ Thymine dimer), cuts out sequence all around damage (big section) and replace all 3. Mismatch repair- mistakes in DNA REPLICATION, DNA polymerase mistake, DNA polymerase can proofread, however can still miss mistakes, this is why we need to understand type of damage. Fixed in same way as nucleotide incision repair 4. Homologous recombination- repairs double strand breaks, worst case scenario, (radiation/also happens everyday normally), best option for repair, uses second copy of DNA to copy back the correct information “homologous chromosome” only occurs after DNA replication, must have two copies of DNA info already 5. Non-homologous end joining- also repairs double strand breaks, happens BEFORE DNA replication, when another copy unavailable. Ends get trimmed and stuck back together, can cause mutations, last resort but if cell left like that it will die GENETIC TESTING BRCA gene: 30% of all breast cancers and also a percentage of ovarian cancer Patient DNA 3 billion base pairs, and we want a copy of one gene out of that