10. Transcription

Transcription in Prokaryotes

Multiple Choice
Which of the following is not an example of a prokaryotic promoter sequence?
Multiple Choice
What is the purpose of a sigma factor in prokaryotic transcription?
Multiple Choice
Prokaryotic transcription can create polycistronic mRNA.
Open Question
The diagram below shows a DNA duplex. The template strand is identified, as is the location of the nucleotide.

Assume this region contains a gene transcribed in a bacterium. Identify the location of promoter consensus sequences and of the transcription termination sequence. <>
Open Question
The DNA sequences shown below are from the promoter regions of six bacterial genes. In each case, the last nucleotide in the sequence (highlighted in blue) is the nucleotide that initiates transcription. Determine the consensus sequence for the Pribnow box from these sequences. <>
Open Question
Bacterial and eukaryotic gene transcripts can differ—in the transcripts themselves, in whether the transcripts are modified before translation, and in how the transcripts are modified. For each of these three areas of contrast, describe what the differences are and why the differences exist.
Open Question
Describe the two types of transcription termination found in bacterial genes. How does transcription termination differ for eukaryotic genes?
Open Question
Draw a bacterial promoter and label its consensus sequences. How does this promoter differ from a eukaryotic promoter transcribed by RNA polymerase II? By RNA polymerase I? By RNA polymerase III?
Open Question
The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following; 3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5' 5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3' Label the template and coding DNA strands.
Open Question
The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following; 3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5' 5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3' Draw the mRNA structure that forms during transcription of this segment of the TrpA gene.
Open Question
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 typse leads to intrinsic termination of transcription.
Open Question
Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?
Open Question
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 atWhat 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.)
Open Question
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 at42°C
Open Question
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 at40°C