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BIOCHEM2280 - FINAL EXAM Brandl's Lectures (Topics 22 - 28).docx

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Biochemistry 2280A
Chris Brandl

Brandls Lectures Topic 22Gene Regulation Human genome encodes 25000 different protein encoding genes In any one cell type 10000 are expressed at various levels Expression of the correct genes is essential for growth and differentiation of all cellsDifferent cell types express different genes these differences make the tissues what they are due to proteins Whats the significance of gene expressiono Many diseases are due to altered expression of one or more genes o By manipulating gene expression we have the potential to prevent or reverse diseases DNA is transcribed to RNA and ultimately translated to become protein Central Dogma gene expression in the simplest way Central Dogma defines two key processes in gene expression 1 Transcription copying of DNA into RNA 2 Translation process of decoding an RNA to synthesize proteinFirst principle step at which genes can be regulated is at transcription 1 Initiation 2 Elongationrate at which RNA polymerase goes through the gene 3 Termination Second major step is at RNA processingsteps converting a newly transcribed RNA into a molecule that can be translated4 RNA editing5 5 capping 6 Splicing 7 3 Polyadenylation 8 Next step that can regulated is mRNA export made in the nucleus to be functional it has to move out other cytoplasm to be translated o The process that moves it out is highly regulated9 Translation can also be broken down to initiation elongation termination 10 mRNA degradationmany genes are regulated at their level of degradation11 Protein modificationsome proteins are only active if theyre posttranslational modifiedo Translated protein is inactive and something happens to modify it that modified form is active o Some molecules are cleaved to become activeo Essential for gene to be active or effectively expressed12 Genes can also be regulated at protein degradation depends on rate of synthesis and decayo You can control amount of product by rate of decayThose are the 12 different ways that gene can be regulated most simplest terms however there might be more The first step in a biological process is often highly regulated as it saves energy Because transcription is the first step in gene expression it is often a key step in regulationWhy is there an RNA step in gene expression DNARNAProteino RNA step provides an amplification which contributes to genes being expressed at different levelso Because RNA can be degraded expression of a gene can be stopped quickly cant just get rid of the gene information will be lost but if you get rid of the RNA you dont lose the gene o RNA provides additional opportunities to regulate gene expression Topic 23Transcription Prokaryotic transcription has many fundamental mechanisms similar to eukaryotic transcription Promoter DNA sequences required to initiate transcription of a geneoperon recognize RNA polymerase and any gene specific regulatory factorsOperon set of gene transcribed from a single promoter and thus expressed from a common RNA only prokaryotic cellso Group of genes one promoter one terminator typical operon structure Terminator DNA sequence required to stop transcription
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