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Why Control Gene Expression?
Every cell has same genetic infoDifferent cells need to do different thingsGenes need to be turned on and off TERM 2
Control of Gene Expression (simple terms)
DEFINITION 2 Prokaryotes EukaryotesTranscription Factors Enhancers andupstream elements Nucleosomes DNA methylation TERM 3
Transcription Factors
DEFINITION 3 TF are proteins that alter gene expressionActivators - bind DNA and activate (increase) gene expressionRepressors - bind DNA and repress (decrease) gene expressionBind near start of gene with other proteins that alter gene expression TERM 4
Enhancers and upstream elements
DEFINITION 4 Transcription factors that can bind far away from the promoter toDISTAL ENHANCERSUPSTREAM ELEMENTS TERM 5
Nucleosomes
DEFINITION 5 Eukaryotes - chromatin made up of nucleosomesDNA - tightly packaged - harder for transcription factors and RNA polymerase to access it because of this
DNA Methylation
methylation reduces gene expressiontends to occur on CpG islands - upstream of promoters TERM 7
Prokaryotic Gene
Organisation
DEFINITION 7 Prokaryotes have their genes organised into operonsOperon is a genetic unit that encodes one/more related genes that are transcribed as a single,polycistronicmRNAOperons expression is controlled by transcription factors TERM 8
trp Operon
DEFINITION 8 controls production of tryptophan in E coliTrpR is a transcription repressorRepresses transcription of the trp operon when tryptophan is presentTrpR regulates four other operons TERM 9
lac Operon
DEFINITION 9 controls production of lactose in E colilacZ = Beta galactosidase. Cleaves bond between galactose and glucose.LacY = Lactose permease. Transports lactose into the cell.LacA = Betagalactosidasetransacetylase. Role in hydrolysis. TERM 10
more details
DEFINITION 10 Lactose breaks down into > glucose and galactoseE coli prefers metabolisingglucose > lactose
