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22 Gene Expression 2012.docx

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Western University
Biochemistry 2280A
Chris Brandl

Gene Expression DNA the blueprint of life DNA itself is an inert chemical For DNA to be affective it must be expressedIn order to code for life the information within DNA must be expressedThe human genome encodes 25000 different genesIn any one cell type 10000 are expressedThe expression of the correct genes is essential for growth and differentiation of all cellsThe information is stored in DNA in the form of genesSo its dependant on which genes get expressed that makes different cell do different things Eg a muscle cell is different from a liver cell because they each express a different 10 000 genes with some genes overlapping but at least some different onesCorrect gene expression is essential for normal cell health If we have incorrect gene expression will result in diseased phaseOut of the blueprint of life expressed genes is how we define life itself Significance of Gene Expression Most disease states most notably cancer result from or are manifest by alterations in expression of one or more genesBy manipulating gene expression profiles we have the potential to prevent or reverse disease statesSo if we have something expressed in incorrect amount or wrong places will result in diseases and can often be traced back to defects in gene expressionSo if we can change the gene expression profile back to normal we have a good chance of reversing the diseased statemany diseases you can pinpoint one or 2 genes that have altered gene expressionThe Central DogmaSo DNA becomes RNA through transcription and that RNA becomes protein through the process of translation The blue print is DNA which is in most cases converted to protein which is what does the actions Defines two of the steps in gene expression fig 71 Why is there an RNA Step in Gene Expression 1 The RNA step allows genes to be expressed at different levelseach gene is present at a constant level two copies per cell diploidRNA can vary from less than one to over 1000 copies per cell Fig72Simply because we can have a lot more RNA in the cell for one gene type than another type if no RNA intermediate then each gene would be present at constant level that is 2 copies per gene for diploids RNA varies from 1 copy1000 copies so we can get a lot of gene expression by making a lot of RNA we cant do that for DNASo RNA allows for magnification of the single geneThe RNA step provides an amplification which allows genes to be expressed at different levels 2 RNA can be rapidly degraded this allows a quick off signal to stop gene expressionAllows expression of a gene can be stopped quickly because it can be degradedBecause RNA can be easily degraded expression of a gene can be stopped quicklyRNA provides a rapid off switch you cant do that in DNA because then you would lose it forever1 RNA provides additional opportunities for regulation of the expression of genes There are many steps at which genes can be regulatedPoints at which gene expression can be regulated in a eukaryotic cell
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