Concept explainers
For each of the terms in the left column, choose the best matching phrase in the right column.
a. induction | 1. glucose prevents expression of catabolic operons |
b. repressor | 2. protein or RNA undergoes a reversible conformational change |
c. operator | 3. regulates translation of mRNAs in trans |
d. allostery | 4. RNA leader that regulates gene expression in response to a small molecule or ion |
e. operon | 5. site to which repressor binds |
f. catabolite | 6. termination of transcription elongation in repression response to translation |
g. reporter gene | 7. group of genes transcribed into one mRNA |
h. attenuation | 8. negative regulator |
i. sRNA |
9. a fusion of the regulatory region of one gene to the coding region of another gene whose product is assayed readily |
j. riboswitch | 10. stimulation of protein synthesis by a specific molecule |
1.
To determine:
The term that describes “glucose prevents expression of catabolic operons.”
Answer to Problem 1P
Correct answer:
glucose prevents expression of catabolic operons: catabolite repression.
Explanation of Solution
Catabolite repression is seen among microbes when both glucose and lactose are supplied in their growing environment. The presence of glucose suppresses the utilization of lactose.
2.
To determine:
The term that describes “protein or RNA undergoes a reversible conformational change.”
Answer to Problem 1P
Correct answer:
Protein or RNA undergoes a reversible conformational change: allostery.
Explanation of Solution
Allostery means change in the conformation that is associated with the proteins involved in the regulation of a particular gene. The repressor molecule undergoes conformational change, which enables it to be relieved from the operator region and then promote transcription.
3.
To determine:
The term that describes “regulates transcription of mRNA in trans.”
Answer to Problem 1P
Correct answer:
Regulates translation of mRNA in trans: sRNA
Explanation of Solution
sRNA, known as short ribo nucleic acid sequence are trans-acting molecules that regulate the expression of specific genes. When a sRNA molecule binds to the mRNA, it leads to the breakdown of transcribed mRNA molecule by the action of ribonuclease enzyme. The binding of sRNA to the mRNA molecule prevents the formation of stem and loops in the mRNA.
4.
To determine:
The term that describes “RNA leader that regulates gene expression in response to a small molecule or ion.”
Answer to Problem 1P
Correct answer:
RNA leader that regulates gene expression in response to a small molecule or ion: riboswitch.
Explanation of Solution
Riboswitch is an important part of RNA leader sequence that binds to specific molecules called effectors. The formation of stem and loop in the transcript of mRNA molecule plays an important role in the continuation and attenuation of transcription through the riboswitches.
5.
To determine:
The term that describes “site to which repressor binds.”
Answer to Problem 1P
Correct answer:
Site to which repressor binds: operator.
Explanation of Solution
Operator is considered as the important part of the regulatory sequence of the gene. The repressor binds to the operator region of the regulatory gene and suppresses the process of transcription.
6.
To determine:
The term that describes “termination of transcription elongation in repression response to translation.”
Answer to Problem 1P
Correct answer:
Termination of transcription elongation in repression response to translation: attenuation.
Explanation of Solution
Attenuation is a process that controls the regulation of anabolic pathways. When the substrate is available, the transcription continues further and transcribes the functional regions or shrugs off the mRNA completely.
7.
To determine:
The term that describes “group of genes transcribed into one mRNA.”
Answer to Problem 1P
Correct answer:
Group of genes transcribed into one mRNA: operon.
Explanation of Solution
An operon is the set region found in the genome that consists of regulatory, structural, and functional portion. The structural region contains the promoter and operator whereas the functional region codes for the actual protein.
8.
To determine:
The term that describes “negative regulator.”
Answer to Problem 1P
Correct answer:
Negative regulator: repressor.
Explanation of Solution
Repressor is a type of protein molecule which prevents the transcription of the particular gene associated with the regulatory parts of the gene.
9.
To determine:
The term that describes “a fusion of the regulatory region of one gene to the coding region of another gene whose product is assayed readily.”
Answer to Problem 1P
Correct answer:
A fusion of the regulatory region of one gene to the coding region of another gene whose product is assayed readily: reporter gene.
Explanation of Solution
The function of reporter genes is monitored through the regulatory regions of other well studied genes. Due to this reason, the regulatory region of the lactose operon is used in the expression system for analyzing and studying the expression of unknown genes.
10.
To determine:
The term that describes “stimulation of protein synthesis by a specific molecule.”
Answer to Problem 1P
Correct answer:
Stimulation of protein synthesis by a specific molecule: induction.
Explanation of Solution
Induction is associated with the stimulation of protein synthesis by the process of transcription, where specific factor initiates the process of transcription.
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Chapter 16 Solutions
Genetics: From Genes To Genomes (6th International Edition)
- a. What is the function of operons in bacterial gene regulation? b. Describe how a bacterial operon can be regulated by repressible proteins (such as the tryptophan operon). Include in your description both the “on” and “off” states of the operon. Key elements of your diagram should include: Co-repressor, Genes, mRNA, Operator, Operon, Promoter, Repressor, RNA polymerase.arrow_forwardWhen 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_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
- You 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_forwardThe regulator protein that acts on a negative repressible operon is synthesized as a. an active activator. c. an active repressor. b. an inactive activator. d. an inactive repressor.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_forward
- The gad operon is controlled by a number of transcription factors that regulate a promoter of approximately 450bp. Which would NOT explain why bacterial promoters are shorter than the typical eukaryotic promoter? a. Bacteria do not have nucleosomes b. Bacteria do not have mediator complex c. Each operon is regulated by only one signal d. All of the above are truearrow_forwardIn the lac operon, the lac genes are transcribed in the presence of lactose because a RNA polymerase binds to the operator b The repressor can not bind the promoter c Production of the repressor protein is inducible d The inducer binds to the repressor e The inducer binds to the operatorarrow_forwardWhat would occur if the repressor of an inducible operon weremutated so it could not bind the operator?(A) irreversible binding of the repressor to the promoter(B) reduced transcription of the operon’s genes(C) buildup of a substrate for the pathway controlled by theoperon(D) continuous transcription of the operon’s genesarrow_forward
- Which of the following statements uses the term homologous correctly?A. The two X chromosomes in female mammalian cells are homologousto each other.B. The α-tubulin gene in Saccharomyces cerevisiae is homologousto the α-tubulin gene in Arabidopsis thaliana.C. The promoter of the lac operon is homologous to the promoterof the trp operon.D. The lacY genes of E. coli and K. pneumoniae are approximately60% homologous to each other.arrow_forwardDefine the following in the context of operons: a. positive control b. give an example of an operon that is under positive control c. negative control d. give an example of an operon that is under negative control e. repressor f. give an example of a repressor molecule g. activator h. give an example of an activatorarrow_forwardOperon X produces three enzymes that convert Compound A to Compound B. The R gene makes the regulatory molecule for Operon X. Normally, the three enzymes are only produced when Compound B is present. However, when the R gene is mutated (no R gene is made), none of the three enzymes are produced regardless of whether Compount B is absent or present. Is this opern inducible or repressible? Does the R gene produce an activator or repressor? Is the R protein made in an active or inactive form?arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning