MCB 450 1st Edition Lecture 23Outline of Last Lecture I. DNA replication OverviewII. Replication in ProkaryotesIII. Replication in EukaryotesIV. TelomeraseOutline of Current Lecture I. Transcription in prokaryotesa. RNA polymeraseb. Sites of Initiationc. Transcription Elongationd. Transcription terminatione. Transcription Regulation- the lac operonII. Overview of Transcription in EukaryotesCurrent LectureDNA Replication-DNA ligase fills the gaps between the okazaki fragmentsThe Terminator Region Contains One-Way Ter Sites-Ter site cluster is oposite of oriC-Each cluster is a binding site for a Tus proteinProteins involved in DNA Replication in E. coli-Tus protein terminates the replication processEukaryotic cells contain a number of different DNA Polymerases-DNA polymerase-alpha initiates the replication process-Then DNA polymerase-delta will take it overThe End Replication Problem-Every time you replicate DNA the 5' end of your DNA gets shorter and shorterWhat 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 thoughThese 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.oBy using the enzyme telomerase-It works as a reverse transcriptaseTelomerase extends the 3' strands-Most cancer cells can produce telomeraseoThus there cells become immortalExpression of Genetic Information-The RNA transcript will have the same sequence as the non-template strand-Nontemplate strand oSense/coding or positive strand-Template strandoAntisense/non-coding strand or negative strandCore 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 transcriptionThe 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 transcribedThe E. coli RNA polymerase holoenzyme-Orange is the sigma factorTranscription Initiation-Upstream is to the left and downstream is to the rightStrand Elongation Reaction-Phosphodiester linkage is between
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