Genetic Analysis: An Integrated Approach (3rd Edition)
3rd Edition
ISBN: 9780134605173
Author: Mark F. Sanders, John L. Bowman
Publisher: PEARSON
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Textbook Question
Chapter 12, Problem 11P
Explain the circumstances under which attenuation of operon gene expression is advantageous to a bacterial organism. Would you expect attenuation to be found in a single
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In the absence of lactose and the lacI repressor gene is mutated such that the repressor protein product can no longer bind to the operator, the structural genes will: [ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"]
In the presence of lactose and the lacI repressor gene is mutated such that the repressor protein product can no longer bind to the operator, the structural genes will: [ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"]
The attenuation mechanism that helps block expression of the tryptophan operon requires all of the following, except
A) O MRNA transcript of the trp leader sequence
B) Oaribosome stalled at the stop codon of the trp leader transcript
C) O formation of an attenuator loop
D) O low intracellular levels of tryptophan
Suppose you are studying the regulation of a gene involved in the metabolism of two nutrients, Llamasin and Alpacalon, in bacteria. You are trying to determine if these nutrients act as inducers in their operons. The following data were collected from your experiments. Which of these operons is most similar to the lac operon? Explain.
Nutrient
Levels of nutrient in growth medium
Level of transcription of genes in operon
Llamasin
low
high
high
low
Alpacalon
low
low
high
high
Highlight one in green:
Llamasin Alpacalon
Explanation:
Chapter 12 Solutions
Genetic Analysis: An Integrated Approach (3rd Edition)
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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- You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and 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 Say you don’t know which mutant has a defect in the site and which one has a mutation in the binding protein. To figure it out, you construct the two partial diploid strains (i and ii below), and you then assay the levels of the Emu1 and Emu2 proteins in these two strains. F’ (reg1- reg2+ emu1- emu2+) / reg1+ reg2+ emu1+ emu2- F’ (reg1+ reg2- emu1- emu2+) / reg1+ reg2+ emu1+ emu2- What proteins do you predict will be expressed for strains i and ii if reg2 encodes the regulatory protein and reg1 is the regulatory site?arrow_forwardTryptophan (Trp) attenuation is an extra mechanism of regulation of trp operon when trp level is too high. Attenuation causes premature transcription termination. b) Predict what will happen if trp repressor lose its allosteric effect.arrow_forwardIn the presence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the trpR repressor gene is mutated such that the repressor protein product can no longer bind to the operator, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan and the trpR repressor gene is mutated such that the repressor protein product can no longer bind to the operator, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be constantly expressed"]arrow_forward
- A bacterial operon is responsible for the production of the biosyntheticenzymes needed to make the hypothetical amino acidtisophane (tis). The operon is regulated by a separate gene, R.The deletion of R causes the loss of enzyme synthesis. In the wildtypecondition, when tis is present, no enzymes are made; in theabsence of tis, the enzymes are made. Mutations in the operatorgene (O-) result in repression regardless of the presence of tis. Isthe operon under positive or negative control? Propose a modelfor (a) repression of the genes in the presence of tis in wild-typecells and (b) the mutations.arrow_forwardGene 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?arrow_forwardDescribe what would happen to the lac operon in a low-lactose environment and in a high lactose environment. a) How will each of these environments affect gene expression? b) What would happen to the repressor in each case? c) How will each of these environments affect RNA polymerase?arrow_forward
- What are the similarities and differences between DNA Polymerase and RNA polymerase? Explain the process of how the Lactose operon functions in the presence of lactose, glucose, both, and without lactose. Explain the process of how the Tryptophan operon functions in the presence of tryptophan and in the absence of tryptophan. What are the three types of horizontal gene transfer among prokaryotes? How do these three types of horizontal gene transfer work? What are restriction endonucleases, restriction fragments, & explain the general premise behind Recombinant DNA technology. Describe: STR’s, Mitotyping, & SNP’s in relation to DNA profiling What are Transgenic or Genetically Modified Organisms? Provide examples using herbicide tolerance and pest resistance.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_forwardThe lac operon in E. coli bacteria codes for proteins that break down (digest) the disaccharide lactose. Therefore, the lac operon is expressed at its highest levels when there is: A) glucose but no lactose B) lactose and glucose C) lactose but no glucose D) no glucose or lactosearrow_forward
- What experimental results would indicate that the mutation lacISlacIS is dominant to lacI+lacI+? In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a constitutive state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in an activated state in the presence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the presence of lactose.arrow_forwardIn the presence of tryptophan, and a mutation in the allosteric domain that abolishes tryptophan binding______. a) the active repressor cannot bind trp), so operon gene transription is attenuated b) the inactive repressor cannot bind trpO, so operon gene transcription occurs] c) the active repressor binds trpP, so operon gene trasncription is repressed, the inducer cannot bind trpO, so gene transcription occurs d) the repressor binds to the corepressor, and an operon gene transcription occursarrow_forwardWhat is the phenotype of an E. coli strain with a mutation in the lac operator that allows the lac repressor to irreversibly bind the operator? Assume glucose is absent. 1S A) O Transcription of the operon is very high whether lactose is present or not. B) O Transcription of the operon is very low whether lactose is present or not. C) O Transcription of the operon is high in the presence of lactose, and low in its absence. D) O Transcription of the operon is low in the presence of lactose, and high in its absence.arrow_forward
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