Pearson eText Genetic Analysis: An Integrated Approach -- Instant Access (Pearson+)
3rd Edition
ISBN: 9780135564172
Author: Mark Sanders, John Bowman
Publisher: PEARSON+
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Chapter 12, Problem 7P
The trpL region contains four repeated DNA sequences that lead to the formation of stem
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Listed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? a. A mutation that prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTR b. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alanine c. A mutation that creates a stop codon early in region 1 of the mRNA 5′ UTR d. Deletions in region 2 of the mRNA 5′ UTR e. Deletions in region 3 of the mRNA 5′ UTR f. Deletions in region 4 of the mRNA 5′ UTR g. Deletion of the string of adenine nucleotides that follows region 4 in the 5′ UTR
The lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a
single polycistronic mRNA. The new lac strain of Escherichia coli are as shown below:
P+O+Z+Y+A+// P+O+Z+Y+A¯
(i)
Illustrate how lactose induces the gene expression in lac 1 $// I-.
(ii)
Explain the function of the lacP and laco in the bacterial operon.
What would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)
Chapter 12 Solutions
Pearson eText Genetic Analysis: An Integrated Approach -- Instant Access (Pearson+)
Ch. 12 - 12.1 Bacterial genomes frequently contain groups...Ch. 12 - Transcriptional regulation of operon gene...Ch. 12 - Why is it essential that bacterial cells be able...Ch. 12 - Identify similarities and differences between an...Ch. 12 - The transcription of -galactosidase and permease...Ch. 12 - 12.6 Is attenuation the product of an allosteric...Ch. 12 - The trpL region contains four repeated DNA...Ch. 12 - The CAP binding site in the lac promoter is the...Ch. 12 - What role does cAMP play in transcription of lac...Ch. 12 - How would a cap- mutation that produces an...
Ch. 12 - Explain the circumstances under which attenuation...Ch. 12 - Consider the transcription of genes of the...Ch. 12 - Describe the lytic and lysogenic life cycles of ...Ch. 12 - 12.14 Define antisense RNA, and describe how it...Ch. 12 - 12.15 Attenuation of trp operon transcription is...Ch. 12 - 12.16 In the lac operon, what are the likely...Ch. 12 - Identify which of the following lac operon haploid...Ch. 12 - Prob. 18PCh. 12 - 12.19 List possible genotypes for lac operon...Ch. 12 - Suppose each of the genotypes you listed in parts...Ch. 12 - 12.21 Four independent mutants (mutants A to D)...Ch. 12 - Suppose the lac operon partial diploid...Ch. 12 - What is a riboswitch? Describe the riboswitch...Ch. 12 - 12.24 A repressible operon system, like the trp...Ch. 12 - 12.25 What is the likely effect of each of the...Ch. 12 - 12.26 Suppose that base substitution mutations...Ch. 12 - 12.27 Two different mutations affect. Mutant...Ch. 12 - How would mutations that inactivate each of the...Ch. 12 - The bacterial insertion sequence IS 10 uses...Ch. 12 - For an E. coli strain with the lac operongenotype...Ch. 12 - 12.31 How could antisense RNA be used as an...Ch. 12 - 12.32 Section describes the function of tRNA...Ch. 12 - The following hypothetical genotypes have genes A,...Ch. 12 - 12.34 Northern blot analysis is performed on...Ch. 12 - Prob. 35PCh. 12 - Prob. 36PCh. 12 - 12.37 The electrophoresis gel shown in part (a) is...
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- Mutation in the regulatory gene in the lac operon results in the formation of an inactive repressor. List and explain the effect of such a mutation on the expression of the structural gene for lactose in E.coli?arrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. You are given a new strain of Escherichia coli with the following lac operon genotype: p+0°Z•Y*A +// P*O*Z*Y+ A- (i) Explain how the lac I gene affects gene expression. (ii) Explain the function of the lacP in the bacterial operon. (iii) Which part of the lac operon is cis-dominant? Explain.arrow_forwardArginine is one of the amino acids that serves as a building block for protein synthesis. Arginine biosynthesis depends on the expression of the arg operon, which encodes ArgC (a reductase) and ArgB (acetylglutamate kinase). Which of the following statements regarding mutation of the arginine biosynthesis repressor ArgR is true? O A 1-bp insertion in the argR gene would result in a mutant able to grow in the absence of arginine, O A 1-bp deletion in the argB gene would result in a mutant unable to transcriptionally regulate the arg operon encoding argB. O A 1bp insertion in the argC gene would result in a mutant able to grow in the absence of arginine. O A 1-bp deletion in the argR gene would result in a mutant that represses the arg operon when grown in the presence of arginine. None of the above.arrow_forward
- Lactose permease is encoded by the lacY gene of the lac operon.Suppose a mutation occurred at codon 64 that changed the normalglycine codon into a valine codon. The mutant lactose permease isunable to function. However, a second mutation, which changescodon 50 from an alanine codon to a threonine codon, is able torestore function. Is each of the following terms appropriate or inappropriate to describe this second mutation?A. ReversionB. Intragenic suppressorC. Intergenic suppressorD. Missense mutationarrow_forwardThe lac genotypes are as shown below: P+OcZ-Y+A+// P¯O+Z+Y+A+ (i) The lac operon consists of three structural genes, lacZ, lacY and lacA. Which structural genes are involved in lactose metabolism? Explain. (ii) Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote. (iii) What is the function of the promoter in the bacterial operon?arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. Consider each genotype below and complete the table using “+” to indicate that the gene is expressed, and “−” to indicate that gene is not expressed.arrow_forward
- What would happen if the operator sequence of the lac operon contained a mutation that prevented the repressor protein from binding the operator? (Explain what would happen both in the presence and absence of lactose)arrow_forwardSuppose the tRNA synthetase responsible for attaching tryptophan to tRNA is muted in a bacterial strain with the result that the tRNA sythetase functions at twice the efficiency of the wild-type tRNA synthetase. Which of the following is most likely? a)the attenuation mechanism will not function normally and transcriptionof the trp operon will be less dependent upon intracellular tryptophan levels b)the attenuation mechanism will not function normally and transcriptionof the trp operon will be strongly dependent upon intracellular tryptophan levelsarrow_forwardThe dlagram below represents the tryptophan operon with the trp leader MRNA transcript enlarged to represent the AUG transiation start codon, two consecutive tryptophan amino acld codons (UGGUGG), and 4 regions (1, 2, 3, and 4) that base pair to form different hairpin-loop structures in the MRNA leader region. What would happen in this MRNA leader region when cells encounter very low levels of tryptophan in Its environment? Leader region trpE trpD trpC trpB trpA DNA 5' 3' Transcription trp leader sequence mRNA UGGUGG (tryptophan codons) AUG UUUUUU 1 3 4. The translating ribosome would stall at the two tryptophan codons, causing the formation of a hairpin-loop botween regions 3 and 4 to promote transcription of the trp operon. The translating ribosome would stall at the two tryptophan codons causing formation of hairpin-loop between regions 2 and 3, which functions as an anti-lerminator of transcription The translating ribosome would stall at the two tryptophan codons causing formation…arrow_forward
- In the lac operon system, do the inducers act at the transcription or translation level? Explain why it acts in that level in a short but concise way.arrow_forwardAs diagrammed below, some amino acid biosynthetic operons have stem loop structures in the mRNA. These structures play a role in the regulation of the operon by which of the following mechanisms? Translation stop codon- Attenuator loop. mRNA 5' 3' DNA attenuator trpE O Catabolite repressor protein can bind and prevent the hairpins from forming thus allowing translation to occur. O The leader sequence shown contains codons for the amino acid. When these are low, the ribosome stalls, allowing a hairpin between the two middle regions to form so that the rest of the message can be translated. In the presence of large amounts of the amino acid, the hairpin will wind around the amino acid and prevent further translation. O A repressor protein made of that amino acid will bind to the region and prevent translation when large amounts of the amino acid are present. O The uridine-rich region has codons for that amino acid; when present, this region will be a terminator region. The hairpins allow…arrow_forwardThe streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forward
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