Study Guide And Solutions Manual For Genetic Analysis: An Integrated Approach
3rd Edition
ISBN: 9780134832258
Author: Mark F. Sanders, John L. Bowman, Peter Mirabito
Publisher: PEARSON
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Textbook Question
Chapter 12, Problem 25P
What is the likely effect of each of the following mutations of the trpLregion on attenuation control of trp operon gene transcription? Explain your reasoning.
a. Region
b. Region
c. The entire
d. The start (AUG) codon of the
e. Two
f. Twenty nucleotides are inserted into the trpLregion immediately after the polypeptide stop codon.
g. Ten nucleotides are inserted between regions
h. Two nucleotides are inserted immediately following the polypeptide start codon
i. The entire polypeptide coding sequence of trpLis deleted.
j. The eight uracil nucleotides immediately following region
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. a. How many ribosomes are required (at a minimum)for the translation of trpE and trpC from a singletranscript of the trp operon?b. How would you expect deletion of the two tryptophan codons in the RNA leader to affect theexpression of the trpE and trpC genes?
Gene expression in bacteria is controlled by the operon model.
a) Why is the operon model important?
b) Why is the trp operon known as a repressible operon?
You have isolated two different mutants (reg1 and reg2) causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site.
Is the DNA-binding protein a positive or negative regulator of gene expression? Explain.
To determine which mutant has a defect in the site and which one has a mutation in the binding protein, you decide to do an analysis using F′ plasmids. Assuming you can assay levels of the Emu1 and Emu2 proteins, what results do you predict for the two strains (i and ii; see descriptions below) if reg2 encodes the regulatory protein and reg1 is the regulatory site? Explain.
F′ (reg1− reg2+ emu1− emu2+)/reg1+ reg2+ emu1+ emu2−
F′ (reg1+ reg2− emu1− emu2+)/reg1+ reg2+ emu1+ emu2−
Chapter 12 Solutions
Study Guide And Solutions Manual For Genetic Analysis: An Integrated Approach
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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- Suppose 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_forwardYou have isolated two different mutants (reg1 andreg2) causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in aDNA-binding site, and the other has a loss-of-functiondefect in the gene encoding a protein that binds tothe site.a. Is the DNA-binding protein a positive or negativeregulator of gene expression?b. To determine which mutant has a defect in the siteand which one has a mutation in the binding protein, you decide to do an analysis using F′ plasmids. Assuming you can assay levels of the Emu1and Emu2 proteins, what results do you predict forthe two strains (i and ii; see descriptions below) ifreg2 encodes the regulatory protein and reg1 is theregulatory site?i. F′ (reg1−reg2+emu1−emu2+)/reg1+reg2+emu1+emu2−ii. F′ (reg1+reg2−emu1−emu2+)/reg1+reg2+emu1+emu2−c. What results do you predict for the two strains(i and ii) if reg1 encodes the regulatory proteinand reg2 is the regulatory site?arrow_forwardMany bacterial genes with related functions are arranged in operons, sets of contiguous genes that are under the control of a single promoter and are transcribed together. (a) What is the advantage of this arrangement? (b) How might eukaryotic cells, which do not contain operons, ensure the simultaneous transcription of different genes?arrow_forward
- You then make a screen to identify potential mutants (shown as * in the diagram) that are able to constitutively activate Up Late operon in the absence of Red Bull and those that are not able to facilitate E. Coli growth even when fed Red Bull. You find that each class of mutations localize separately to two separate regions. For those mutations that prevent growth even when fed Red Bull are all clustered upstream of the core promoter around -50 bp. For those mutations that are able to constitutively activate the operon in the absence of Red Bull are all located between the coding region of sleep and wings. Further analysis of each DNA sequence shows that the sequence upstream of the promoter binds the protein wings and the region between the coding sequence of sleep and wings binds the protein sleep. When the DNA sequence of each is mutated, the ability to bind DNA is lost. Propose a final method of gene regulation of the Up Lateoperon using an updated drawn figure of the Up Late…arrow_forwarda. The original constitutive operator mutations in thelac operon were all base changes in o1. Why doyou think mutations in o2 or o3 were not isolated inthese screens?b. Explain how a mutagen that causes small insertions could produce an ocmutation.c. Would a strain with one of the ocmutations described in part (b) and also a lacIS mutation be ableto make β-galactosidase either in the presence orabsence of inducer? Explainarrow_forwardIf glucose is not available, but lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?arrow_forward
- In the topic about prokaryotic gene expression regulation, we learned about the LacI-, LacIS, and LacOc mutations. Based on your knowledge of allosteric regulation, invent and describe a hypothetical mutation that would produce constitutive expression of the Lac operon but is not a mutation that occurs in the Lac operator (that is, it must be a different mutation than a LacOc type mutation) and is not a mutation to the DNA binding domain of LacI (that is, it must also be a different mutation than a LacI- type mutation). Clearly mention where in the prokaryotic genome this mutation would occur, and explain the logic behind how that mutation would produce constitutive Lac operon expression.arrow_forwardIf β-galactosidase is expressed when lactose is absent, what does this suggest about the lac operon? a) There is a mutation in the repressor protein b) There is a mutation in the catabolite activator protein c) There is a mutation in the promoter region d) There is a mutation in the luxI proteinarrow_forwardIn addition to observing similarities to the lac operon, you also notice that this gene is regulated via attenuation, similar to the trp operon. Based on this similarity to this model operon, you could state that ___________. Group of answer choices If a terminator loop forms in the DNA, the expression of the structural genes is halted. The formation of the terminator hairpin followed by a series of Uracil (UUUUUUU) functions similar to Rho-Independent termination to result in the stopping of transcription. The transcription of a leader sequence affects the translation of the structural genes. Never mind – all of these statements are true! Attenuation will be the primary means of transcriptional regulation, with a repressor used as a back up option.arrow_forward
- Explain why (a) inactivation of the O2 or O3 sequence of the lac operon causes only a twofold loss in repression, and (b) inactivation of both O2 and O3 reduces repression ∼70-fold.arrow_forward. 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? Q. A mutation that prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTRarrow_forwardIf glucose levels in the cell are high and lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?arrow_forward
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