10.29.09_DiscHmwk - catabolic pathways breaking down a...

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Intro Bio 151/153 Discussion Homework; week of 11/2-11/6 Name: Josh Litwicki Discussion Section #: 609 1a. Draw the lac operon and label all the important parts. b. How is the lac operon regulated? Under what conditions is the operon transcribing mRNA? Under what conditions is the operon not transcribing mRNA (is repressed)? The lactose operon is regulated by the presence of lactose in the medium. If lactose is present, it enters the cell and is converted into allolactose. The allolactose then binds to the repressor of the lactose operon which causes the operon to begin transcription of the lacZ, lacY, and lacA genes. 2. a. Is the metabolic pathway underlying the lac operon catabolic or anabolic? Explain your answer. The lactose operon is catabolic because enzymes in the lactose pathway are inducible enzymes that usually function in
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Unformatted text preview: catabolic pathways, breaking down a nutrient into simpler molecules. b. Is the repressor protein produced in an active or inactive form? The repressor is produced in an active form. c. How does the repressor change from active to inactive? The presence of allolactose causes the repressor to become inactive by binding to the active site and changing the shape of the repressor, making it unable to bind to the operator. 3. What advantages are gained by having genes organized into operons? There is one single switch which the cell uses to control the production of many genes. The cell only allows production when the cell needs it so it does not expend unneeded energy. 1...
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