Microbiology: An Evolving Science (Fourth Edition)
4th Edition
ISBN: 9780393615098
Author: John W. Foster, Joan L. Slonczewski
Publisher: W. W. Norton & Company
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Chapter 10.2, Problem 4TQ
Summary Introduction
To review:
The preferred use of IPTG (isopropyl β-D-thiogalactopyranoside) in order to induce lacZYA operon.
Introduction:
IPTG is a chemical reagent with a similar structure to lactose. It is used in the induction of transcription in lac operon and further induction of protein expression at high levels. Catabolic repression is a phenomenon in which repression of lac operon occurs because glucose acts as a preferred carbon source instead of lactose and thus, glucose directly induces transcription.
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Students have asked these similar questions
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)
Under what conditions would you expect to see high levels of expression of the structural genes in the lac operon?
Group of answer choices
Lactose is absent and glucose is absent
Lactose is absent and glucose is present
Lactose is present and glucose is present
None of these
Lactose is present and glucose is absent
If an abnormal repressor protein could still bind allolactose but the binding of allolactose did not alter the conformation of the repressor protein, how would the expression of the lac operon be affected?
Chapter 10 Solutions
Microbiology: An Evolving Science (Fourth Edition)
Ch. 10.1 - Prob. 1TQCh. 10.2 - Prob. 1TQCh. 10.2 - Prob. 2TQCh. 10.2 - Prob. 3TQCh. 10.2 - Prob. 4TQCh. 10.2 - Prob. 5TQCh. 10.3 - Prob. 1TQCh. 10.3 - Prob. 2TQCh. 10.4 - Prob. 1TQCh. 10.5 - Prob. 1TQ
Ch. 10.5 - Prob. 2TQCh. 10.6 - Prob. 1TQCh. 10 - Prob. 1RQCh. 10 - Prob. 2RQCh. 10 - Prob. 3RQCh. 10 - Prob. 4RQCh. 10 - Prob. 5RQCh. 10 - Prob. 6RQCh. 10 - Prob. 7RQCh. 10 - Prob. 8RQCh. 10 - Prob. 9RQCh. 10 - Prob. 10RQCh. 10 - Prob. 11RQCh. 10 - Prob. 12RQCh. 10 - Prob. 13RQCh. 10 - Prob. 14RQCh. 10 - Prob. 1TQCh. 10 - Prob. 2TQCh. 10 - Prob. 3TQCh. 10 - Prob. 4TQ
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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
- Imagine 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_forwardIn the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answerarrow_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
- In most experiments using the lac operon, researchers use the synthetic inducer IPTG to turn on operon expression, instead of lactose or allolactose. What do you think is the advantage of using IPTG?arrow_forwardGive all possible genotypes of a lac operon that produces, or fails to produce, β-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose absent Lactose present β-Galactosidase Permease β-Galactosidase Permease a. − − + + b. − − − + c. − − + − d. + + + + e. − − − − f. + − + − g. − + − +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 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?arrow_forward
- 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 proteinarrow_forwardA mutant strain of E. coli has a premature stop mutation in the lacZgene, resulting in a non-functional b-galactosidase. Otherwise, all other parts of the operon are functional. Which component of an F' plasmid will restore normal regulation and function of the lac operon in the resulting partial diploid?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
- 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_forwardSuppose 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:arrow_forwardWhat are the effects of the following conditions on Lac operon of bacteria? Please do not forget to mention about the role of repressor, activator, RNA polymerase in each case. Glucose is absent and lactose is present Glucose is present and lactose is present Glucose is present and lactose is absentarrow_forward
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