Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 2 25 15 Notes DNA Replication Part 2 I II DNA synthesis A RNA primase is a type of RNA polymerase B RNA polymerase synthesizes RNA C DNA polymerase synthesizes DNA D DNA ligase joins the gaps between Okazaki fragments E The main enzyme is DNA polymerase III they were numbered in order of discovery F DNA polymerase is involved in proofreading G DNA polymerase II and III are both involved in DNA repair proofreading Structure of DNA polymerase dimer A DNA polymerase functions as a dimer 2 enzymes work together B the sliding clam holds the DNA while alpha added nucleotides on it increases processivity decreases chances that DNA polymerase and DNA will let go of each other decreases chances of error C brings in the nucleotides to extend the DNA D can detect damage right then and there and can repair it so DNA polymerase does not have to essentially does the same thing as DNA polymerase but it can fix it right there if misses an error DNA polymerase II comes in to fix it E Simple gamma complex brings in the ATP that is used during the process of DNA elongation F Processivity is the frequency with which an enzyme dissociates from the template during DNA replication extends the nucleotides G H Without good DNA replication all organisms would face many mutations III IV V Dimeric function of DNA polymerase A The 2 DNA polymerases have to coordinate and end at the same time B The 2 DNA polymerases more together one works to add onto the leading strand while one works to add onto the lagging strand Replisome A Replisome consists of the DNA polymerase III dimer helicase RNA primase single stranded binding proteins B DNA polymerase I and DNA ligase are NOT found in the replisome Termination of DNA replication A Eukaryotes have multiple origins of replication 1 B Replication is always bi directional happens in both directions C Only 1 origin of replication in prokaryotes and it has 2 lagging strands and 2 leading strands D The termination sequence forms a screw like structure Ends of DNA are not completely replicated A RNA primers on both the lagging strands and the leading strands the lagging strand has several primers because it is broken up into pieces and the leading strand has 1 primer because it is all 1 piece B Without a primer DNA polymerase is lacking C The gaps shorten the DNA overtime every time the DNA is replicated it gets shorter and shorter gets shorter because DNA polymerase cannot replace the primers at the ends D This shortened is one of the biggest parts of aging as you age your DNA shortens E Telomeres try to fix this problem Telomere structure and function A Telomeres are present at the very end of the DNA B Every time a cell divides a telomere is lost this loss does not occur in cancer cells so cancer cells survive longer than regular cells and are able to take over parts of the body also telomeres are not lost in stem cells C The process of aging is partly due to losing telomeres overtime D Dolly The Sheep s surrogate mother looked very different than Dolly E Dolly died prematurely Telomerase function A Telomeres recruit telomerase B Telomerase brings in an RNA primer telomerase is just like an RNA primase VI VII VIII 2
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