Wild-type E. coli grows best at 37°C but can grow efficiently up to 42°C. An E. coli strain has a mutation of the sigma subunit that results in an RNA polymerase holoenzyme that is stable and transcribes at wild-type levels at 37°C. The mutant holoenzyme is progressively destabilized as the temperature is raised, and it completely denatures and ceases to carry out transcription at 42°C. Relative to wild-type growth, characterize the ability of the mutant strain to carry out transcription at 40°C

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following:

3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5'

5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3'

Explain how a sequence of this type leads to intrinsic termination of transcription.

Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?

Wild-type E. coli grows best at 37°C but can grow efficiently up to 42°C. An E. coli strain has a mutation of the sigma subunit that results in an RNA polymerase holoenzyme that is stable and transcribes at wild-type levels at 37°C. The mutant holoenzyme is progressively destabilized as the temperature is raised, and it completely denatures and ceases to carry out transcription at 42°C. Relative to wild-type growth, characterize the ability of the mutant strain to carry out transcription at What term best characterizes the type of mutation exhibited by the mutant bacterial strain? (Hint: The term was used in Chapter 4 to describe the Himalayan allele of the mammalian C gene.)

Wild-type E. coli grows best at 37°C but can grow efficiently up to 42°C. An E. coli strain has a mutation of the sigma subunit that results in an RNA polymerase holoenzyme that is stable and transcribes at wild-type levels at 37°C. The mutant holoenzyme is progressively destabilized as the temperature is raised, and it completely denatures and ceases to carry out transcription at 42°C. Relative to wild-type growth, characterize the ability of the mutant strain to carry out transcription at 42°C

Wild-type E. coli grow best at 37°C but can grow efficiently up to 42°C. An E. coli strain has a mutation of the sigma subunit that results in an RNA polymerase holoenzyme that is stable and transcribes at wild-type levels at 37°C. The mutant holoenzyme is progressively destabilized as the temperature is raised, and it completely denatures and ceases to carry out transcription at 42°C. Relative to wild-type growth, characterize the ability of the mutant strain to carry out transcription at 37°C

Write a paragraph describing the abbreviated chemical reactions that summarize RNA polymerase-directed transcription.

A mutant strain of Salmonella bacteria carries a mutation of the rho protein that has full activity at 37°C but is completely inactivated when the mutant strain is grown at 40°C. Are all mRNAs affected by the rho protein mutation in the same way? Why or why not?

A mutant strain of Salmonella bacteria carries a mutation of the rho protein that has full activity at 37°C but is completely inactivated when the mutant strain is grown at 40°C. Speculate about the kind of differences you would expect to see if you compared a broad spectrum of mRNAs from the mutant strain grown at 37°C and the same spectrum of mRNAs from the strain when grown at 40°C.