PS10_solutions - Required problems: PS 10 Answer Key 1. In...

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Required problems: PS 10 Answer Key 1. In what two different ways do bacteria "sense" the amount of trp in the environment? List both, and describe *one* mechanism in detail. One way bacteria “senses” the amount of trp in the environment is by attenuation. If there is a lot of trp in the environment the ribosome moves fast and the 1 pairs with 2 and 3 pairs with 4 to form the transcription termination complex. This complex is the two hairpins followed by a sequence of U’s and terminates transcription. If there is little trp in the environment, the ribosome stalls and instead 2 pairs with 3, which means the transcription conformation is not formed and thus transcription continues. Another way bacteria “senses” the amount of trp in the environment is through the allosteric domain of trpR binding to trp. TrpR is the repressor of trp. When trp-trpR complex forms the repressor is active. But since the repressor is not usually bound to trpO the default is for the trp operon to be “on”. Therefore if there’s a lot of trp you don’t need more trp so you can turn it off by TrpR. 2. What are two hypotheses for the functions of RNA silencing (i.e. RNAi)? Be brief.
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This note was uploaded on 12/02/2011 for the course PCB 3063 taught by Professor Marta during the Fall '08 term at University of Florida.

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PS10_solutions - Required problems: PS 10 Answer Key 1. In...

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