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4. Bio313_2006_gene+regulation2

4. Bio313_2006_gene+regulation2 - Genetic Switches...

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Genetic Switches Mechanism which turns genes on and off in response to a variety of signals Consists of specific DNA sequences located near the transcription start site of a gene and the regulatory proteins that bind to them. Prokaryotic switches – simple repressors (negative control) and activators (positive control) Eukaryotic switches - complex
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Switching genes off and on in bacteria: the lac operon lac operon encodes proteins required to transport lactose into the cell and break it down Bacteria prefer glucose to lactose as a carbon source Changes in the media composition result in changes in co-factor concentrations: + lactose =high allolactose, which binds to lac repressor and removes it from DNA + glucose = low cyclic AMP, no cAMP binding to CAP activator results in its dissociation from the DNA
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