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THE LAC OPERON |  | |||||
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The lac operon is the classic example of gene regulation, in which the production of ß-galactosidase (lactase) is induced by the presence of lactose in the growth medium. In this practical task, ONPG, rather than lactose is used as a substrate for the enzyme. After partial disruption of the cell membrane with methylbenzene (toluene), colourless ONPG is added. The ONPG moves into the cells where it is broken down by the enzyme to form ONP, which is yellow-coloured in alkaline conditions. Both a quick qualitative method using colonies of bacteria scraped from a plate and a slower, quantitative method are described in this section. | ||||||
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Copyright © National Centre for Biotechnology Education, 2005 | www.ncbe.reading.ac.uk | ||
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