Back
Problem 1
Based on discussion in this chapter, What is a gene?
Problem 1
Based on discussion in this chapter, Why are genes for rRNA and tRNA considered to be genes even though they do not produce polypeptides?
Problem 2
In one to two sentences each, describe the three processes that commonly modify eukaryotic pre-mRNA.
Problem 3
Answer these questions concerning promoters. What role do promoters play in transcription?
Problem 4
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 to form mRNA in a eukaryote. Identify the location of the most common promoter consensus sequences. <>
Problem 4
The diagram below shows a DNA duplex. The template strand is identified, as is the location of the nucleotide. If this region is a eukaryotic gene transcribed by RNA polymerase III, where are the promoter consensus sequences located? <>
Problem 4
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. <>Problem 4
Identify similarities and differences between an inducible operon and a repressible operon in terms of
the transcription-regulating DNA sequences.Problem 5
The following is a portion of an mRNA sequence: 3'-AUCGUCAUGCAGA-5' During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.
Problem 5
The following is a portion of an mRNA sequence: 3'-AUCGUCAUGCAGA-5' Write out the sequence and polarity of the DNA duplex that encodes this mRNA segment. Label the template and coding DNA strands.
Problem 5
The following is a portion of an mRNA sequence: 3'-AUCGUCAUGCAGA-5' Identify the direction in which the promoter region for this gene will be located.
Problem 6
Compare and contrast the properties of DNA polymerase and RNA polymerase, listing at least three similarities and at least three differences between the molecules.
Problem 7
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. Examine these sequences and identify the Pribnow box sequence at approximately -10 for each promoter.
Problem 7
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. <>
Problem 8
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.
Problem 9
Describe the two types of transcription termination found in bacterial genes. How does transcription termination differ for eukaryotic genes?
Problem 10
What is the role of enhancer sequences in transcription of eukaryotic genes? Speculate about why enhancers are not part of transcription of bacterial genes.
Problem 11
Describe the difference between introns and exons.
Problem 12
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?
Problem 13
For a eukaryotic gene whose transcription requires the activity of an enhancer sequence, explain how proteins bound at the enhancer interact with RNA pol II and transcription factors bound at the promoter.
Problem 14
Three genes identified in the diagram as A, B, and C are transcribed from a region of DNA. The 5'-to-3' transcription of genes A and C elongates mRNA in the right-to-left direction, and transcription of gene B elongates mRNA in the left-to-right direction. For each gene, identify the coding strand by designating it as an 'upper strand' or 'lower strand' in the diagram. <>
Problem 15
The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.
Illustrate the R-loop structure that would be seen with electron microscopy.Problem 15
The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.
Label the introns.Problem 15
The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.
Are intron regions single stranded or double stranded? Why?Problem 16
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.
Problem 16
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.
Problem 16
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.
Problem 20
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°CProblem 20
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 40°CProblem 20
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 42°C
