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Kathleen Gilmour

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march 22nd 2011UNIT2 Gene RegulationWHY IS UNDERSTANDING REGULATION THE KEY TO UNDERSTANDING SO MUCH OF LIFE1Changes in environment or changes in nutrients2Changes in make up of cell is response to signals3In a multicellular organism cellular differentiation4Conserve energyGene regulation refers to the regulation of activity and may occur at any level While the main control is at the level of transcription additional controls are at the posttranscriptional translational and posttranslational levelsRegulation of Gene Expression in Prokaryotestranscriptional control how to load RNA polymerase to TATA box and what are the factors that interact with DNA to stop that or push that to happenReflects life history reversible responses to the environment are observedRNA polymerase binds to a DNA sequence 5 to the promoter gene Within may be the consensus sequence 5TATAAT3 called a TATA boxRepressor proteins binding to other regulatory DNA sequences may prevent the gene from being expressed block or diminish transcription can be reversed by induction or derepressionActivator proteins binding to other regulatory DNA sequences may turn on expression of the gene bind and boost transcriptionRepressors and activators may regulate the same geneIn prokaryotes many genes are organized into clusters transcription units that areimplicated in a single functionAt a smaller scale many genes are organized into operons one or more operons may be found within a transcription unit ooperon can be considered as a unit of transcription with several genes controlled by a single promoterooperon is a cluster of genes and DNA sequences involved in their regulationoRNA polymerase binds at the promoter and transcribes all the genes in the operon into one mRNA called polycistronic because it contains several cistronsan older definition of a gene used in geneticso630 to 700 operons in E coli examples lac operon for lactose metabolism 3 genes and the trp operon genes for tryptophan biosynthesis 5 geneslac Operon for Lactose Metabolism3 genes trp5 genescollection of genes single spot for transcription one polycistronic message contains 3 genescistron secondary structure and binding of proteins can influence which gene is binded the mostsome operons in which 3 genes are found and the 2 gene is binded the most because it has a goodsequence and the secondary structure allows translation end with 3 potential proteins
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