2. What is the advantage to the cell of having specialized sigma factors that re

Question

2. What is the advantage to the cell of having specialized sigma factors that recognize unique promoter sequences? 4 pts 3. Assume that a specific, mutant strain of E. coli has the normal spacing between the-10 and -35 elements in the promoter upstream of the MerT gene. Which of the following would you expect? 2 pts a. Normal, increased expression only in the presence of mercury. b. Constitutive expression of the MerT gene. c. No expression of the MerT gene. d. decreased expression of the gene in the presence of mercury.

Explanation / Answer

Solution:

2. Sigma factors are subunits of the DNA-dependent RNA polymerase holoenzyme from eubacteria that are required for initiation of transcription at specific promoters. Sigma factors therefore bind to the nonspecific core RNAP and convert the enzyme into a form that is specific for initiation. These specialized Sigma factors that recognize unique promoter sequences would result in specific engagement of RNAP with duplex DNA at the beginning of genes (promoters) as well as efficient initiation of transcription. Also by virtue of such an arrangement they would inhibit nonspecific transcription.

3. a

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