Genetics Chapter 16 Multiple Choice

1. 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

1. 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

1. 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.

1. If there are mutations that inactivate lacP and lacI, which of the following is TRUE? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator) a. These are mutations that are, respectively, cis- and trans-acting on lac operon expression. b. These are mutations that are, respectively, trans- and cis-acting on lac operon expression. c. These will affect the expression of I only. d. These will affect the expression of only Z, Y, and A. e. These mutations will have no effect.

a. These are mutations that are, respectively, cis- and trans-acting on lac operon expression.

1. 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

1. 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

1. 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

1. 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

1. 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.

1. 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

1. 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.

1. 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

1. 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

26. A mutant E. coli strain, grown under conditions that normally induce the lac operon, produces high amounts of ß-galactosidase. What is a possible genotype of the cells? a. lacI+ lacP+ lacO+ lacZ- lacY+ lacA+ b. lacI+ lacP+ lacOc lacZ+ lacY+ lacA+ c. lacI- lacP+ lacO+ lacZ- lacY+ lacA+ d. lacI+ lacP- lacO+ lacZ+ lacY+ lacA+ e. lacI- lacP- lacO+ lacZ- lacY+ lacA-

b. lacI+ lacP+ lacOc lacZ+ lacY+ lacA+

1. 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

1. 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

32. The formation of 1+2 and 3+4 secondary structures of 5′ UTR region mRNA from the trp operon is triggered when a. the tryptophan level inside the bacterial cell is extremely low. b. the tryptophan level inside the bacterial cell is high. c. the repressor protein fails to bind to the operator. d. there is a spontaneous mutation introduced into the 5′ UTR. e. the structural gene transcription within the trp operon gets initiated.

b. the tryptophan level inside the bacterial cell is high.

30. If a mutation prevents the formation of the antiterminator 2+3 loop in the trp operon, what would be the effect? a. Transcription only when tryptophan is absent b. Transcription only when tryptophan is present c. Constitutive attenuation of transcription d. Constitutive transcription e. No effect, as 2+3 loop has no function

c. Constitutive attenuation of transcription

1. 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

1. 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. 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.

33. RNA molecules that are complementary to particular sequence on mRNA are called a. complementary RNA. b. sense RNA. c. antisense RNA. d. riboswitches. e. ribozymes.

c. antisense RNA.

1. 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

1. 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

1. 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.

1. 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. As the transcription will require an activator protein, the transcription will be turned off. e. More cAMP will be produced in a cell to compensate for the lack of an activator protein.

d. As the transcription will require an activator protein, the transcription will be turned off.

1. 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

31. The trp operon is known to operate by both negative repressible regulation of operator and attenuation. Which of the following does NOT support the reason as to why dual control exists to regulate the operon? a. The repression alone is never complete, and some transcription can be initiated. b. Combined mechanism provides a much finer tuning of tryptophan synthesis regulation. c. Attenuation and repression allow the cell to more sensitively respond to the tryptophan level. d. It is most likely due to the fact that the attenuation is the evolutionary relic, which by accident has remained. e. Repression responds to the cellular levels of tryptophan, while attenuation responds to the number of tRNA charged with tryptophan.

d. It is most likely due to the fact that the attenuation is the evolutionary relic, which by accident has remained.

34. Which of the following facts about riboswitches is INCORRECT? a. Binding of certain molecules to the riboswitches results in the formation of specific secondary structures of mRNA. b. Certain molecules that bind to riboswitches may act as repressors or inducers of transcription. c. Riboswitches are only found in bacterial cells but not in archaeal, fungal, or plant cells. d. Riboswitches are typically found in the 3′ UTR of the mRNA structure. e. The secondary structure that forms riboswitches typically contains a base stem and several branching hairpins.

d. Riboswitches are typically found in the 3′ UTR of the mRNA structure.

27. A mutant E. coli strain, grown under conditions that normally induce the lac operon, does not produce ß-galactosidase. What is a possible genotype of the cells? a. lacI+ lacP+ lacO+ lacZ+ lacY- lacA+ b. lacI+ lacP+ lacOc lacZ+ lacY+ lacA+ c. lacl+ lacP+ lacO+ lacZ+ lacY+ lacA+ d. lacI+ lacP- lacO+ lacZ+ lacY+ lacA+ e. lacI_ lacP+ lacO—lacZ+ lacY+ lacA-

d. lacI+ lacP- lacO+ lacZ+ lacY+ lacA+

29. Which of the following secondary structures causes attenuation of structural genes of the trp operon? a. 1+2 b. 1+3 c. 2+4 d. 2+3 e. 3+4

e. 3+4

1. 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.

1. 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.

28. Transcriptional control that acts by regulating the continuation of transcription is called a. riboswitching. b. antitermination. c. negative control. d. operator mutation. e. attenuation.

e. attenuation.

35. RNA-mediated repression is carried out by a. nonsense RNA. b. sense RNA. c. antisense RNA. d. riboswitches. e. ribozymes.

e. ribozymes.

1. 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