Topic 4 - Topic 4: Gene Regulation Gene expression in...

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Topic 4: Gene Regulation Gene expression in bacteria can be regulated at the level of transcription initiation (the synthesis of mRNA and the level of translation ( synthesis of protein. In both induction and repression a small molecule enters the cell and changes the gene expression. Ex: the development of cancer is often due to a mutation in a protein regulator, removing the ability of the protein to regulate cell growth. 4.1 Environmentally Regulated Gene Expression Constitutively expressed genes are genes that are expressed all the time, such as genes for RNA polymerase subunits, ribosome components, and amino acyl tRNA synthetises are all constitutively expressed. Environmentally regulated genes are only expressed at high levels under certain environmental conditions Enzyme production is controlled at the level of initiation of gene transcription 4.2 Lac Operon LacI is bound to the beginning of the lac operon when there is no lactose in the cell. This prevents DNA polymerase from transcribing the gene. This process is called negative regulation Lactose is composed of 2 sugars, glucose and galactose, covalently bonded together to form a disaccharide. Genes are smaller case 1
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Topic 4 - Topic 4: Gene Regulation Gene expression in...

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