Microbiology: An Introduction
12th Edition
ISBN: 9780321929150
Author: Gerard J. Tortora, Berdell R. Funke, Christine L. Case
Publisher: PEARSON
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Textbook Question
Chapter 8, Problem 3A
Pseudomonas has a plasmid containing the mer operon, which includes the gene for mercuric reductase. This enzyme catalyzes the reduction of the mercuric ion Hg21 to the uncharged form of mercury, Hg0. Hg21 is quite toxic to cells; Hg0 is not.
- a. What do you suppose is the inducer for this operon?
- b. The protein encoded by one of the mer genes binds Hg21 in the periplasm and brings it into the cell. Why would a cell bring in a toxin?
- c. What is the value of the mer operon to Pseudomonas?
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If the above gene is one of the three structural genes of the lac operon that codes for the protein/ enzyme responsible for breaking lactose into two molecules of simple sugars, what triggers the activation of this gene?
a.
Absence of Inhibitory protein
b.
Presence of lactose
c.
Absence of lactose
d.
Presence of Inhibitory protein
e.
Absence of Regulatory protein
Let’s suppose you have isolated a mutant strain of E. coli in which the lac operon is constitutively expressed. In other words, the operon is turned on in the presence or absence of lactose. One possibility is that the mutation may block the transcription of the lacI gene, thereby preventing the synthesis of lac repressor. A second possibility is that the mutation could alter the sequence of the lac operon in a way that prevents the repressor protein from binding to the operator. How would you distinguish between these two possibilities?
If 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 protein
Chapter 8 Solutions
Microbiology: An Introduction
Ch. 8 - Briefly describe the components of DNA, and...Ch. 8 - DRAW IT Identify and mark each of the following on...Ch. 8 - Match the following examples of mutagens. Column A...Ch. 8 - The following is a code for a strand of DNA. a....Ch. 8 - Identify when (before transcription, after...Ch. 8 - Which sequence is the best target for damage by UV...Ch. 8 - You are provided with cultures with the following...Ch. 8 - Why are mutation and recombination important in...Ch. 8 - NAME IT Normally a commensal in the human...Ch. 8 - Match the following terms to the definitions in...
Ch. 8 - Match the following terms to the definitions in...Ch. 8 - Feedback inhibition differs from repression...Ch. 8 - Bacteria can acquire antibiotic resistance by all...Ch. 8 - Suppose you inoculate three flasks of minimal...Ch. 8 - Plasmids differ from transposons in that plasmids...Ch. 8 - Mechanism by which the presence of glucose...Ch. 8 - The mechanism by which lactose controls the lac...Ch. 8 - Two offspring cells are most likely to inherit...Ch. 8 - Which of the following is not a method of...Ch. 8 - Nucleoside analogs and ionizing radiation are used...Ch. 8 - Replication of the E. coli chromosome takes 40 to...Ch. 8 - Pseudomonas has a plasmid containing the mer...Ch. 8 - Ciprofloxacin, erythromycin, and acyclovir are...Ch. 8 - HIV, the virus that causes AIDS, was isolated from...Ch. 8 - Human herpesvirus-8 (HHV-8) is common in parts of...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- 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)arrow_forwardIf a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??arrow_forwardImagine that a new strain of E. coli is discovered, and it contains the following novel genetic region including the lacI gene and the lac operon: *see image* Upstream of the promoter associated with the lac operon, there is a new operator element "Oν" (O-"nu"). This new operator has high sequence homology to O1, the DNA element that is bound with the highest affinity by the lac repressor. What would be the impact of this new genetic element regarding behavior of the operonin the absence (vs. the presence) of lactose and allolactose? Answer in terms of the protein levels of the lac repressor, as well as the proteins encoded by the genes lacZ/Y/A in the downstream region of the operon. Remember that proteins, once expressed/generated, will not persist forever, and that they have a natural lifetime (ending when they are degraded by the cell).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? 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′ UTRarrow_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_forwardYou 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_forward
- What would happen to the regulation of the tryptophan operon in bacterial cells that express a mutant form of the tryptophan repressor that (1) cannot bind to DNA, (2) cannot bind tryptophan, or (3) binds to DNA even in the absence of tryptophan?arrow_forwardA graduate student studying the pathogenic bacteria Acinetobacter baumannii made cDNA from planktonic cells and biofilm cells and performed RNA-Seq on both samples. She aligned her sequencing reads to a locus of the baumannii genome as shown. a. Which genes are on an operon together? Explain which data supports this? b. What is the most expressed transcript from the locus in Planktonic culture? c. Order the transcripts from largest increase in relative expression between biofilm and planktonic cells to the largest decrease in relative expression. d. When this data was compared to microarray transcriptional profiling, the microarray data provided lower expression levels for the most highly expressed transcripts. Why did this occur?arrow_forwardLet’s suppose you have isolated a mutant strain of E. coli in which the lac operon is constitutively expressed. In other words, the operon is turned on in the presence or absence of lactose. One possibility is that the mutation mayblock the transcription of the lacI gene, thereby preventing the synthesis of lac repressor. A second possibility is that the mutation could alter the sequence of the lac operator in a way that prevents lac repressor from binding to the operator. How would you distinguish between these two possibilities?arrow_forward
- If 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_forwardThere is Hyaluronic acid synthesis occuring in Group X Strep and it is controlled by an operon with 3 genes, called hasXYZ. Based on the 3-line diagram model, a. How many ribosome binding sites are there for the protein? b. How many promoters are there for the genes? c. How many start codons are there for the protein? d. How many RNA Polymerase binding locations are there for the genes? e. How many proteins will be fully functional? f. How many mRNA strands are made?arrow_forwardA strain of E. coli has the genotypes shown below at the lac operon, where I = regulator gene, P = promoter, O = operator, Z = βgalactosidase gene, and Y = permease gene. The superscript+ indicates a wild-type allele,c indicates a constitutive mutation, and− indicates a defective mutation. For each genotype, indicate whether the enzyme will be synthesized or not synthesized when lactose is present or absent by placing a + for synthesis occurring and a − for synthesis not occurring in the appropriate blank. Explain your reasoning for each answer.arrow_forward
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