BOLOGY 107 Lecture 27 Outline of Last Lecture I DNA Structure a Watson and Crick b Genetic Material c DNA Replication Outline of Current Lecture II DNA Replication a Polymerases b Proofreading c Eukaryote problem III Gene Expression a Central Dogma b Transcription Current Lecture DNA Replication 1 Polymerases i Require template old DNA strand ii Samples nucleotide triphosphate until the proper hydrogen bonds form iii Attaches nucleotide to the 3 OH of previous base releases a pyrophosphate 2 phosphates b Primase RNA polymerase i Primase lays down RNA primer 1 Builds a short strand of RNA c DNA Polymerase III Pol III i Starts DNA off of RNA primer ii Builds from 5 to 3 1 Two strand of old DNA become separate for leading and lagging strands a Leading strand matches the direction needed for replication replicated in a continuous strand b Lagging strand is opposite direction for replication replicated in sections These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute i Okazaki fragments sections of DNA curved to replicate in the proper direction leapfrogged 1 Need cleaned up from RNA primers to start each jump d DNA Polymerase I Pol I i Removes RNA fragments and replaces them with DNA fragments e DNA Ligase i Bonds spaces in DNA where chain stops 2 Proofreading a Contemporaneous with synthesis and subsequent to synthesis b If Pol III places improper base it can step back and attach proper base i Sensed by a distortion in helic shape c Mistake can be cut out by Pol I later d Change becomes permanent if not corrected before DNA is replicated again 3 Eukaryote problem a Linear DNA has ends because the RNA primer is needed to start the new strand DNA is cut from the front each replication i Telomere stretch of repetitive sequence at the end of a chromosome ii Telomerase extends repetitive sequence using its own RNA template Gene Expression b Small change in DNA can lead to a large phenotype change 4 Central Dogma a Information flows from DNA to RNA to proteins i Transcription DNA information to RNA ii Translation RNA information to proteins 1 In bacteria happen in the same place and time 2 In eukaryotes different place and time a Transcription nucleus translation cytoplasm b Universal system used by all cells 5 Transcription a Uses DNA as a template i RNA polymerase makes RNA 5 to 3 based off of DNA detaches at bases DNA re associates with other strand 1 Initiation Elongation Termination
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