Biology 1001A Study Guide - Final Guide: Dna Mismatch Repair, Dna Ligase, Transposase

• School: Western University
• Department: Biology
• Course: Biology 1001A
• Professor: Tom Haffie

Document Summary

Mechanism of proofreading: polymerase can only continue if most recently added base is correctly paired. Polymerase reverses using built-in deoxyribonuclease to remove the nucleotide. Enzyme then resumes moving forward, inserting the correct nucleotide: error rate: 1 mispair / 1 million nucleotides. Mechanisms of mismatch repair: correct a-t and g-c pairs fit perfectly between sugar-phosphate backbones, mispai(cid:396)ed (cid:271)ases a(cid:396)e too (cid:271)ig/s(cid:373)all a(cid:374)d (cid:272)a(cid:374)"t fo(cid:396)m hydrogen bond characteristic of the normal base pairs. Distort structure of dna helix: repair enzyme: Moves along double helix scanning for distortions. Removes portion of new chain: ne(cid:449) st(cid:396)a(cid:374)d is(cid:374)"t (cid:373)ethylated yet so it"s disti(cid:374)guisha(cid:271)le f(cid:396)o(cid:373) te(cid:373)plate st(cid:396)a(cid:374)d. However: methylation can occur before repair enzyme (50/50 chance) Dna ligase seals chain to continuous dna molecule: also repairs alterations caused by chemicals/radiation/uv. Relative distribution of various components of genome sequence (junk vs. essential dna: 55% t(cid:396)a(cid:374)sposo(cid:374)s, (cid:448)i(cid:396)uses, a(cid:374)d a fe(cid:449) (cid:862)dead ge(cid:374)es(cid:863) (cid:894)pseudoge(cid:374)es(cid:895, 25% unknown (likely junk, 10% intron (junk, 10% essential (2% proteins)