Concept explainers
Videos
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then
- A. the amino acid inactivates the repressor.
- B. the repressor is active in the absence of the amino acid.
- C. the amino acid acts as a corepressor.
- D. the amino acid turns on transcription of the operon.
Introduction:
Operon refers to the functional unit of the DNA (genomic). It consist of various genes that controls operon’s regulation. There are two types of operons; lac (lactose) and Trp (tryptophan).
Answer to Problem 1TYU
Correct answer:
If a particular operon encodes certain enzymes for forming an amino acid and is regulated as Trp operon, then the amino acid will be acting like a corepressor molecule. Therefore, option (C) is correct.
Explanation of Solution
Reason for the correct statement:
A Trp operon is a group of genes, which encodes certain enzymes (biosynthetic) for tryptophan. This is expressed when the levels of tryptophan is low. An operon that encodes certain enzymes for the formation of amino acids and acts like a Trp operon, then, the amino acids will act like a corepressor. A corepressor is a small molecule that cooperates with the repressor protein for switching the operon off.
Option (C) is given as “the amino acid acts as a corepressor”.
“If a particular operon encodes certain enzymes for forming an amino acid and is regulated as Trp operon, then the amino acid will be acting like a corepressor molecule”, it is the right answer.
Hence, the option (C) is correct.
Reasons for the incorrect statements:
Option (A) is given as “the amino acid inactivates the repressor”.
The amino acid will be acting like a corepressor, hence it will not inactivate the repressor, and however it will react with the repressor. So, it is a wrong answer.
Option (B) is given as “the repressor is active in the absence amino acid”.
If the operon has to be kept ON, then the repressor will be inactive in the absence of amino acid. So, it is a wrong answer.
Option (D) is given as “the amino acid turns on the transcription of operon”.
The amino acid is not responsible for turning the transcription ON. So, it is a wrong answer.
Hence, options (A), (B), and (D) are incorrect.
The amino acid will be acting like a corepressor molecule as if a particular operon encodes certain enzymes for forming an amino acid and is regulated as the Trp operon.
Want to see more full solutions like this?
Chapter 15 Solutions
Campbell Biology in Focus, Books a la Carte Edition; Modified Mastering Biology with Pearson eText - ValuePack Access Card - for Campbell Biology in Focus (2nd Edition)
Additional Science Textbook Solutions
Human Physiology: An Integrated Approach (7th Edition)
Laboratory Manual For Human Anatomy & Physiology
MARINE BIOLOGY
Biological Science
Fundamentals of Anatomy & Physiology Plus Mastering A&P with eText - Access Card Package (10th Edition) (New A&P Titles by Ric Martini and Judi Nath)
- A mutation at the operator prevents the regulator protein from binding. What effect will this mutation have in the following types of operons? a. Regulator protein is a repressor of a repressible operon. b. Regulator protein is a repressor of an inducible operon.arrow_forwardWhat is the role of a substrate that controls a repressible operon? a. increase the production of inactive repressor proteins b. bind to the repressor protein and activate it c. bind to the repressor protein and deactivate it d. bind to the promoter region and decrease the affinity of RNA polymerase for the promoterarrow_forwardIn the lac operon, how would gene expression be affected if each one of the following segments was missing? A. lac operon promoter B. Operator site C. lacA genearrow_forward
- Theara operon is an inducible operon that controls the production of the sugar arabinose. When arabinose is present in a bacterium it binds to the protein AraC, and the complex binds to the initiator site to promote transcription. In this scenario, AraC is a(n) ________. a. activator b. inducer c. repressor d. operatorarrow_forwardStudy the depiction of the lac operon in Figure 11.2. Normally, the genes are turned off when lactose is not present. Lactose activates the genes, which code for enzymes that enable the cell to use lactose. Mutations can alter the function of this operon. Predict how the following mutations would affect the function of the operon in the presence and absence of lactose: a. mutation of regulatory gene; repressor will not bind to lactose b. mutation of operator; repressor will not bind to operator c. mutation of regulatory gene; repressor will not bind to operator d. mutation of promoter; RNA polymerase will not attach to promoterarrow_forwardYou are growing E. coli in a laboratory in order to study their operons. The growth media you are using contains lactose, no glucose and no tryptophan. Using your knowledge of operons and their regulation a.Which operons would be functional under these conditions? b.What repressors would be made? (NOTE: name the repressors using their gene names) c.Which repressor(s) would be made in the inactive form? d.Which repressor(s) would be made in the active form? e.Which repressor(s) under these conditions can bind the operator sequence? f.Which repressor(s)under these conditions cannot bind the operator sequence?arrow_forward
- If lactose isn't present in the environment of an E. coli, what is the state of the lac operon? O a. It is "on" (high transcription) because will glucose will still be present, so the operon's products will be needed. O b. It is "on" (high transcription) because CAP will be bound to the promoter O c. It is "off" (no transcription) because RNA polymerase will be inactivated d. It is "off" (no transcription) and the repressor will be bound to the operatorarrow_forwardWhich of the following statements about trp operon regulation is TRUE? A. Low trp levels result in trp repressor binding. O B. High trp levels result in transcriptional antitermination. C. Low trp levels cause the ribosome to fall off at the trp codons in the upstream ORF. O D. High trp levels cause the ribosome to fall off at the trp codons in the upstream ORF. O E. Low trp levels result in transcriptional antitermination. QUESTION 34 Consider the following partial diploid for the lac operon system. lacl+ O+ lac Z+Y-A- lacls O+ 1. 2. lac Z-Y+ A+ In this configuration, which of the following statements is TRUE? A. With no lac present, ZYA will all be expressed. B. with lac present none of the genes (ZYA) will be expressed. O C. With no lac present, only YA will be expressed. D. None of these answers is correct. E. With no lac present, only Z will be expressed.arrow_forwardHow does the lac operon regulate lactose digestion in bacteria?a. The repressor protein becomes a lactose-digesting enzyme onlywhen lactose is present.b. The repressor protein binds to the lac operon when lactose ispresent, blocking transcription.c. When lactose is present, it binds to the operator region of the lacoperon, activating transcription of the repressor protein gene.d. The repressor protein falls off the lac operon when lactose ispresent, and lactose-digesting genes are expressed.arrow_forward
- When iron is scarce, some bacteria can stop synthesis of all enzymes that require iron (Fe3+), such as superoxide dismutase (SOD). Which of the following accurately describes a mechanism for this regulation? Mark all that apply. A. Regulation occurs by an inducible operon B. When absent, the lack of iron causes the repressor to deactivate and block the promoter region for these genes C. Regulation occurs by a repressible operon D. When present, iron binds and activates the repressor proteinarrow_forwardAn operon is repressible—a small effector molecule turns off itstranscription. Which combination(s) of small effector molecule andregulatory protein could be involved in this process?A. An inducer plus a repressorB. A corepressor plus a repressorC. An inhibitor plus an activatorD. An inducer plus an activatorarrow_forwardIn the trp operon, tryptophan is best characterized as being a: A. repressor B. inducer C. corepressor D. DNA-binding domainarrow_forward
Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning