BIO206H5 Lecture Notes - Lecture 17: Lac Repressor, Regulatory Sequence, Operon
Document Summary
Review from last lecture: e. coli is a cell that demonstrates a preference for glucose compared to other sugars. The gene regulatory system is directed got make glucose the default sugar. In the absence of glucose, many di and tri and polysaccharide components can be used as a sugar source. Expression of genes: trade-off between how cells are used in glucose vs when lactose is present is absent. Genes can be negatively regulated or positively regulated. There is a protein (a repressor protein) that binds to a gene regulatory sequence near the promoter, blocks binding of rna polymerase and prevent transcription from happening. Another repressor: a protein that binds to dna but only binds to dna when it has a small molecule bound to it. (protein-small molecule complex) only in this case does it bind, blocking transcription. This is therefore relieved once the small molecule is relieved.