How would you describe the effect a repressor has on the lac operon when lactose is present.?

1 Answer
Joëlle
Aug 1, 2016

In that situation the repressor has no effect.

Explanation:

The lac operon is an ingenious genetic system bacteria use for the production of metabolism and transport of lactose. Three genes in this operon are regulated together in a very efficient way.

In the absence of lactose the repressor binds to a certain region (the operator) of the operon. This inhibits transcription of the operon, because RNA polymerase can't bind.

http://bio1151.nicerweb.com/Locked/media/ch18/lac_repressed.html
In the presence of lactose the repressor is inactivated. A molecule similar to lactose (allolactose) binds to the repressor releasing it from the operator. Now the RNA polymerase can bind to start transcribing the genes.

http://bio1151.nicerweb.com/Locked/media/ch18/lac_induced.html

This way the genes are only expressed when needed!

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