MCB 450 1st Edition Lecture 23 Outline of Last Lecture I DNA replication Overview II Replication in Prokaryotes III Replication in Eukaryotes IV Telomerase Outline of Current Lecture I Transcription in prokaryotes a RNA polymerase b Sites of Initiation c Transcription Elongation d Transcription termination e Transcription Regulation the lac operon II Overview of Transcription in Eukaryotes Current Lecture DNA Replication DNA ligase fills the gaps between the okazaki fragments The Terminator Region Contains One Way Ter Sites Ter site cluster is oposite of oriC Each cluster is a binding site for a Tus protein Proteins involved in DNA Replication in E coli Tus protein terminates the replication process Eukaryotic cells contain a number of different DNA Polymerases DNA polymerase alpha initiates the replication process Then DNA polymerase delta will take it over The End Replication Problem Every time you replicate DNA the 5 end of your DNA gets shorter and shorter What are Telomeres Telomere region is not used to encode for a gene When the telomere gets too short this signals to the cell that it is time to either enter apoptosis or senescence Each cell has a limited number of times that it can replicate Stem cells have a way of getting around this though 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 o By using the enzyme telomerase It works as a reverse transcriptase Telomerase extends the 3 strands Most cancer cells can produce telomerase o Thus there cells become immortal Expression of Genetic Information The RNA transcript will have the same sequence as the non template strand Nontemplate strand o Sense coding or positive strand Template strand o Antisense non coding strand or negative strand Core Bacterial RNA Polymerase Beta and Beta are the workhorse part of the polymerase 5 subunits make the core enzyme Need the sigma portion to initiate transcription The alpha subunit recognizes and binds to the promoter The right are coding strands There is no zero site The stronger the RNA polymerase binds to the promoter the more likely that strand of RNA is going to be transcribed The E coli RNA polymerase holoenzyme Orange is the sigma factor Transcription Initiation Upstream is to the left and downstream is to the right Strand Elongation Reaction Phosphodiester linkage is between nucleotides
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