Under the system of genetic control of the trp operon A when

Under the system of genetic control of the trp operon. A. when there are high levels of tryptophan in the medium, transcription of the trp operon occurs at high levels. B. when there is no tryptophan in the medium, transcription of the trp operon occurs at high levels. C. when there are high levels of tryptophan in the medium, transcription of CAP occurs at high levels. D. when there are high levels of tryptophan in the medium, ribosomes \"stall\" and reduce the levels of tryptophan synthesized. E. when cAMP levels are decreased. A researcher mixes heat killed (lysed) S cells and with living R cells and DNase. He then injects the mixture into a mouse. The likely result is: A. The mouse lives and no bacterial cells are found in its blood. B. The mouse lives and living R cells are found in its blood. C. The mouse dies and living S cells are found in its blood. D. The mouse dies and living R cells are found in its blood. E. None of the above

Solution

12) In trp operon, group of enzymes code for the biosynthesis of the enzyme tryptophan. trp operon i seen in bacteria like E.coli. The trp operon icludes 5 genes (trpA, trpB, trpC, trpD and trpE) along with promotor and operator. Promotor region binds with RNA polymerase and operator region binds with repressor protein. When the tryptophan levels are high, the repressor protein binds to the operator site and stops the expression of the operon and when the tryptophan levels are low, the repressor protein no longer binds with the operator region and the operon is turned on and expresses its enzymes.

Therefore, the answer for this question is option (B) when there is no tryptophan in the medium, transcription of trp operon occurs at high levels.