Chapter 16 Flashcards
Which of the following statement about regulation of gene expression is correct?
a. An inducible gene is transcribed when a specific substance is absent.
b. A gene is any DNA sequence that is transcribed into an mRNA molecule only.
c. All genes are transcribed at all times as long as they have a functional promoter.
d. The regulation of gene expression is the same in both eukaryotes and prokaryotes.
e. The regulation of gene expression is critical for the control of life processes in all organisms.
e. The regulation of gene expression is critical for the control of life processes in all organisms.
Which of the following generally get transcribed constitutively?
a. Regulatory gene
b. Structural gene
c. Operator element
d. Promoter element
e. Operon
b. Structural gene
Which of the following types of eukaryotic gene regulation is at the level of DNA?
a. Alternation of chromatin structure
b. mRNA processing
c. RNA interference
d. mRNA stability
e. Post-translational modification
a. Alternation of chromatin structure
Which of the following DNA binding motifs are composed of three alpha helices?
a. Zinc-finger
b. Leucine-zipper
c. Homeodomain
d. Helix-turn-helix
e. Helix-loop-helix
c. Homeodomain
Proteins with DNA binding motifs predominantly bind to the ____________ of DNA.
a. major grooves
b. minor grooves
c. paired nitrogenous bases
d. phosphate groups
e. deoxyribose sugar
a. major grooves
Which of the following statements about DNA binding protein is NOT true?
a. Specific amino acids within the motif form hydrogen bonds with DNA.
b. These proteins can affect the expression of a gene.
c. Most DNA binding proteins bind dynamically.
d. Some of these proteins incorporate metal ion such as zinc.
e. Once bound, most of DNA binding proteins remain on DNA permanently.
e. Once bound, most of DNA binding proteins remain on DNA permanently.
Which of the following statements about gene regulation concerning operon is INCORRECT?
a. A repressible gene is controlled by a regulatory protein that inhibits transcription.
b. For a gene under negative repressible control, a small molecule is required to prevent the gene’s repressor from binding to DNA.
c. For a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator.
d. A regulator gene has its own promoter and is transcribed into an independent mRNA.
e. Presence of operon where genes of related functions are clustered is common in bacteria, but not in eukaryotes.
b. For a gene under negative repressible control, a small molecule is required to prevent the gene’s repressor from binding to DNA.
When binding of the inducer to the repressor causes a conformational change, which then prevents the repressor from binding to DNA, the repressor is called a(n) __________ protein.
a. coactivator
b. allosteric
c. structural
d. operating
e. responsive
b. allosteric
The________ is a type of regulator protein that binds to a region of DNA in the promoter of a gene called the operator and prevents transcription from taking place.
a. inducer
b. repressor
c. activator
d. inactivator
e. terminator
b. repressor
An example of a gene product encoded by a regulatory gene is
a. beta-galactosidase enzyme.
b. allolactose.
c. repressor protein.
d. an operator.
e. a terminator.
c. repressor protein.
E. coli lac operon control by CAP is
a. negative inducible.
b. negative repressible.
c. positive inducible.
d. positive repressible.
e. regulated by riboswitches.
c. positive inducible.
An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule. The type of control illustrated is
a. negative inducible.
b. negative repressible.
c. positive inducible.
d. positive repressible.
e. catabolite repression.
b. negative repressible.
An operon is controlled by a repressor. When the repressor binds to a small molecule, it is released from binding to DNA near the operon. The operon is never expressed if a mutation prevents the repressor from binding to the small molecule. The type of control illustrated is
a. negative inducible.
b. negative repressible.
c. positive inducible.
d. positive repressible.
e. attenuation.
a. negative inducible.
What is the function of allolactose in regulation of the lac operon?
a. Inducer
b. Repressor
c. Activator
d. Promoter
e. Regulatory protein
a. Inducer
What is the function of cAMP in regulation of the lac operon?
a. It activates a repressor protein.
b. It activates an activator protein.
c. It inactivates a repressor protein.
d. It inactivates an activator protein.
e. It causes attenuation.
b. It activates an activator protein.
In the absence of tryptophan, what happens to the genes within the trp operon?
a. The regulator without tryptophan-binding prevents the genes from being transcribed.
b. The regulator falls off the operator and structural genes get transcribed.
c. Lack of tryptophan increases the level of cAMP high, which leads to activation of CAP protein and gene expression.
d. The active repressor binds to the operator and genes do not get transcribed.
e. The active activator binds to the operator and transcription of structural gene takes place.
b. The regulator falls off the operator and structural genes get transcribed.
When a structural gene is under positive inducible control, what would be the result of a mutation that eliminates the activator protein?
a. The structural gene to be constitutively expressed due to the lack of inducible control.
b. The transcription of structural gene will not be affected, as an activator is not required.
c. The mutation will lead to activation of a repressor upon the lack of an activator protein, which will block transcription.
d. d. As the transcription will require an activator protein, the transcription will be turned off.
e. e. More cAMP will be produced in a cell to compensate for the lack of an activator protein.
d. d. As the transcription will require an activator protein, the transcription will be turned off.
When a structural gene is under negative inducible control, what would be the result of a mutation that eliminates the repressor protein?
a. The structural gene will be constitutively expressed due to the lack of negative inducible control.
b. The transcription of the structural gene will not be affected, as a repressor is not required.
c. The mutation will lead to activation of an activator upon the lack of a repressor protein, which will allow the transcription to continue.
d. As the transcription will require a repressor protein, the transcription will be turned off.
e. More cAMP will be produced in a cell to compensate for the lack of a repressor protein.
a. The structural gene will be constitutively expressed due to the lack of negative inducible control.
What would happen to the lac operon in the absence of allolactose?
a. The structural genes within the lac operon the will be constitutively transcribed.
b. The activator protein will be bound to the operator, which will turn on the structural gene behind it.
c. The repressor regulator protein binds to the operator and prevents the transcription of the structural gene.
d. The catabolite activator protein becomes inactivated and no transcription occurs.
e. The cAMP level rises in the absence of allolactose, which in turn inactivates the transcription.
c. The repressor regulator protein binds to the operator and prevents the transcription of the structural gene.
A promoter that affects only genes that are on the same piece of DNA is referred to as a ____-acting promoter.
a. cis
b. trans
c. enhancer
d. positive
e. negative
a. cis
It is possible for a repressor to negatively regulate the expression of an operon because
a. the repressor induces the expression of the inducer by binding to the promoter that comes before the inducer gene.
b. one of the structural genes expressed in the operon negatively regulates the repressor.
c. the repressor-binding site overlaps the promoter site of the operon, allowing it to physically block the binding of RNA polymerase.
d. the repressor-binding site on the DNA overlaps with the translation start site, hence preventing the transcription.
e. the repressor physically blocks where the activator should be binding on the operator region.
c. the repressor-binding site overlaps the promoter site of the operon, allowing it to physically block the binding of RNA polymerase.
E. coli lac operon control by lacI is
a. negative inducible.
b. negative repressible.
c. positive inducible.
d. positive repressible.
e. attenuation.
a. negative inducible.
Where would the lac repressor be bound in a (nonmutant) E. coli cell that is growing in low glucose and high lactose? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator)
a. P
b. O
c. P and O
d. I, P, O
e. The repressor would not be bound
e. The repressor would not be bound
Which parts of the DNA region shown in the diagram encode proteins? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator)
a. P
b. I, P, O
c. P, O, Z, Y, A
d. I, Z, Y, A
e. I, P, O, Z, Y, A
d. I, Z, Y, A
