Exam 3 Prep Flashcards
Genetic regulatory proteins bind to the DNA.
Transcription
Repressor proteins bind to an mRNA and prevent ribosome binding.
Translation
A transcription terminator forms in the RNA.
Transcription
Riboswitches produce an RNA conformation that prevents ribosome binding.
Translation
Antisense RNA binds to the mRNA.
translation
The product of a metabolic pathway inhibits the first enzyme in a pathway.
Post-translation
A protein is covalently modified.
Post-translation
Which gene is responsible for producing the protein that converts lactose to allolactose?
lacZ
Which of the following would NOT be considered a reversible post-translational modification?
Proteolytic processing
Acetylation
Methylation
Phosphorylation
Proteolytic processing
The trpR gene encodes a _____.
Repressor
The trp repressor is bound to the operator when tryptophan levels are _____.
high
The trp operon is also regulated by _____ attenuation.
transcription
Attenuation is similar to rho _____ termination.
independent
The mRNA from the trpL gene forms stem loops as it is being _____.
transcribed
An inducer binds to an activator protein and inhibits transcription. True or False
False
How can antisense RNA inhibit translation?
An antisense RNA binds to a transcript and inhibits translation.
An inhibitor regulates an inducible gene. True or False
False
T/F The lacI gene makes a repressor protein.
T
T/F The structural proteins encoded by the lac operon are involved in lactose synthesis.
F
T/F The CAP protein is an activator that binds to the operator.
F
T/F The product of lacI is an allosteric protein that can undergo a conformational change when allolactose binds to it.
T
T/F CAP binding causes the DNA to bend facilitating RNA polymerase binding.
T
Which of the following sets of conditions would result in high levels of gene transcription from the lac operon?
Low glucose, low lactose High glucose, high lactose Low glucose, high lactose High glucose, low lactose
Low glucose, high lactose
You identify a CAP mutant protein that is constituitively bound to the CAP site.
Under which conditions will the lac operon be transcribed at high levels in cells that contain this mutant protein?
Lactose is present, glucose is not Neither lactose nor glucose is present Lactose and glucose are both present Glucose is present, lactose is not
Lactose is present, glucose is not
Lactose and glucose are both present
If a cell has a mutation in the lacY gene that produces a non-functional product, how is regulation of the lac operon affected?
Multiple Choice
Expression of the lac operon is normal because lacY is not required to produce allolactose. The lac repressor cannot bind to the operator. The lac operon cannot be induced, because lactose cannot enter the cell. The lac operon cannot be transcribed by RNA polymerase because of the lacY mutation.
The lac operon cannot be induced, because lactose cannot enter the cell.
How is the lac operon regulated?
Multiple Choice
It is inducible, under positive control. It is repressible, under negative and positive control. It is repressible, under negative control. It is inducible, under negative and positive control
It is inducible, under negative and positive control
The absence of lactose results in the lac repressor protein _________blank.
Multiple Choice
binding both the DNA and allolactose binding to DNA binding to other lac repressors binding to allolactose
binding to DNA
Transcription of the lac operon results in the production of how many different mRNA transcripts?
1
Attenuation of the trp operon requires which conditions to be met?
Multiple Choice
Tryptophan levels must be low and regions 3 and 4 must pair. Tryptophan levels must be high and regions 2 and 3 must pair. Tryptophan levels must be high, and regions 3 and 4 must pair. Tryptophan levels must be low and regions 2 and 3 must pair.
Tryptophan levels must be high, and regions 3 and 4 must pair.
Translation of mRNA transcribed from the trp operon can be regulated by formation of a secondary structure within the mRNA.
The mRNA that forms this secondary structure is transcribed from which gene in the trp operon?
Multiple Choice
operator trpE trpA trpL
trpL
The presence of a small effector molecule may inhibit transcription. True or False
True
You identify a CAP protein mutant that is unable to bind cAMP.
How will this mutant affect transcription of the lac operon?
Multiple Choice
The lac operon will always be transcribed at a high rate. The lac operon will only be transcribed at a high rate when lactose is present and glucose is not. The lac operon will only be transcribed at a high rate when glucose is present and lactose is not. The lac operon will never be transcribed at a high rate.
The lac operon will never be transcribed at a high rate.
One form of gene expression control found frequently in prokaryotes involves a _____, which occurs when an RNA can exist in two different secondary conformations.
riboswitch
One conformation of the RNA requires a small molecule binding which stabilizes the _____ structure.
secondary
In Bacillus subtilis, a riboswitch controls the _____ of the thi operon involved in thiamin pyrophosphate synthesis.
transcription
Riboswitches can regulate transcription, _____, and RNA stability.
translation
Bacteria use riboswitches extensively; about _____ of bacterial genes are regulated this way.
4%
T/F DNA binding proteins involved in the regulation of gene expression bind covalently and irreversibly to specific DNA sequences.
F
Which of the following interact with DNA in a non-sequence specific manner?
Histones
Sigma factors
both
Histones
T/F Two genes in a bacterial cell may be expressed at different levels, but each individual gene is expressed at the same level under all environmental conditions.
F
A
Regulatory Gene
B
Lac promoter (lac P)
C
LacZ
D
LacY
E
LacA
F
I promoter
G
CAP site
H
Operator site (lac O)
The selection of which chromosome is inactivated is a _____ process.
random
The inactive X chromosome in a human female somatic cell is called a _____.
barr body
Although the Tsix transcript is produced by both X chromosomes the Xist transcript is only produced from the _____ chromosome.
inactive
The symmetry break that occurs is due to localization of _____ to one X chromosome.
CTCFs
Presence of the Xist transcript on the Xi chromosome results in the recruitment of _____.
macro H2A
At least some genes are silenced on inactive X chromosomes by _____.
methylation
Select the functional roles of heterochromatin.
Check All That Apply
Gene silencing Gene silencing Preventing transposition Preventing transposition Preventing viral proliferation Preventing viral proliferation Preventing X-inactivation
Gene silencing Gene silencing
Preventing transposition Preventing transposition
Preventing viral proliferation Preventing viral proliferation
What is a property of a bidirectional enhancer?
Multiple Choice
It can enhance transcription independently of its orientation to the gene. It binds directly to mediator proteins. It is located in the core promoter. It is bound by TFIID.
It can enhance transcription independently of its orientation to the gene
A transcriptional repressor that controls the transcription of gene A is not normally active unless bound by an effector molecule X. In a certain cell, the domain of the repressor that binds X is mutated so that X can no longer be bound.
With all other factors being the same, what effect do you predict on the transcription of gene A if X is added to the cell when it is already transcribing gene A?
The transcription of gene A will not be affected
T/F Maintenance methylation of DNA is rare and highly regulated.
F
If a drug was developed that could inhibit TFIID binding to the core promoter, what would its effect on transcription be?
Transcription that was currently occurring would be finished but there would be no new initiation.
T/F DNA methylation in eukaryotes, which is associated with transcription inhibition, occurs on A residues at GATC sites.
F
The inheritance of traits is sometimes the direct result of specific alleles being present or absent, but it can also be due to the ability of an allele to be _____.
Expressed
The definition of epigenetics is the study of mechanisms of heritable traits that _____ the result of changes in DNA sequence.
are not
In _____ inheritance the transmission of the trait may be based not on the allele but on which parent the allele comes from.
epigenetic
The modifications made to DNA in epigenetics results in changes in _____ association with the DNA.
protein
In epigenetics, change can be due to _____ of DNA.
methylation
Which of the following bonds would mediate the interaction between a regulatory DNA binding protein and the double-stranded DNA?
Non-covalent bonds
Covalent bonds
Both
Non-Covalent bonds
Which of the following is TRUE of alternative sigma factors in E. Coli?
A) Alternative sigma factors bind to promoters with a different -35 sequence element than the main sigma factor (sigma 70)
B) Alternative sigma factors regulate the expression of genes under specific environmental conditions or stresses
C) Alternative sigma factors are always abundant in the cell and bind to the sigma 70 promoter with high affinity.
D) A and B
E) B and C
D
Which of the following sequences does a bacterial depressor bind to ?
Promoter
Operator
Activator
Terminator
Operator
T/F Genes controlled by an activator protein typically have a promoter sequence that has a weak affinity for binding sigma factors.
T
T/F In bacteria, small effector molecules control whether or not repressors and activators bind to DNA
T
When considering gene regulation in bacteria which of the following is TRUE of inducible genes:
A) An inducer will bind to a repressor putting it in a conformation that can bind to the operator
B) Inducible genes are typically involved in catabolic pathways
C) Inducibe genes are only under negative controle
D) A and B
E) B and C
B
If a bacteria gene is regulated by both positive and negative controle which of the following sites would you find the DNA?
A0 Operator site
B) Activator site
C) Effector site
D) A and B
E) A, B, and C
D
In the lac operon consists of three genes: lacZ, lacY, and lac A. How many promoters are required to express these three genes?
1
Which of the following is TRUE of the lac operon when lactose is present?
A) Lactose is converted to allolactose by beta-galactosidase
B) Allolactoswe binds to the repressor protein
C) The repressor protein is in a conformation that binds to the operon
D) A and B
E) A, B, and C
D
Which of the following is true of the positive control when considering the regulation of the lac operon?
A) Adenylyl cyclase is inhibited by glucose
B) If cAMP levels are high the CAP protein will bind to the CAP site in the DNA
C) CAP protein binding to the CAP site in the DNA stabilizes the RNA polymerase at the promotoer
D) A and B
E) A, B, and C
E
Considering the regulation of the lac operon in E. coli which of the following is true when the cell is in the presence of both glucos and lactose?
A) The repressor is not bound to the operator in the DNA
B) CAP is not bound to the CAP site in the DNA
C) There is a high level of transcription of lacZYA
D) A and B
E) A, B, and C
D
Consider and E. coli cell with not lactose present, How many beta-galactosidase molecules are in this E. coli cell?
None
a little
a lot
a little
T/F The trp operon is a repressible operon regulated by both negative and positive controle
F
Which of the following is true when there is an excessive amount of tyrptophan present in the cell?
A) Charged tRNA serves as the corepressor and binds to the repressor protein
B) Free tryptophan serves as the corepressor and binds to the repressor protein
C) The repressor is bound to the corepressor, putting it in a conformation that does NOT bind to the operator
D) A and C
E) B and C
B
What is the purpose of the attenuation mechanism for regulation the trp operon?
To sense the amount of tRNA charged with tryptophan in the cell
Which of the following is involved in the attenuation mechanism in the regulation of the trp operon?
A) A leader region in the mRNA containing codons for Tryptophan
B) Anintrinsic termination signal
C) Coupled transcription-translation
D) A and B
E) A, B, and C
E
Consider the regulation of the trp operon. Which of the following is true when there is not tryptophan present and coupled transcrition-translation is occurring?
A) The repressor is not bound to the operator
B) The ribosome stalls at the Trp-Trp codons in the mRNA molecule
C) An intrinsic termination signal forms in the mRNA
D) A and B
E) A, B, and C
D
Which of the following is a mechanism for modulation the activity of eukaryotic transcription factors?
A) Binding of small molecules
B) Formation of homodimers
C) Covalent modification
E) All of the above
E
What type of genes are constitutive genes?
Genes that are expressed continuously in all cells of an organism, regardless of environmental conditions or the cell’s stage in the cell cycle.
What type of genes are regulated?
Specific metabolic pathways
What would be the most efficient way to regulate a bacterial gene?
Regulate transcription, translation, and post translation
Which of the following is true with regards to enhancer sequences?
A) They are orientation-dependent
B) They may be located either upstream or downstream of the promoter
C) Repressor proteins bind to them
D) They cannot be downstream of the start of transcription
B) They may be located either upstream or downstream of the promoter
What can increase transcription?
Acetylation of histone
Recruitment of SWI/SNF complex
Decreased methylation of DNA
Creation of an NFR
What can decrease transcription?
Removal of core promoter
Increased methylation of DNA
Increased nucleosome density
What are some characteristics of heterochromation?
Stained throughout the entire cell cycle
Attached to nuclear lamina
Inhibits gee expression
More compacted
What are some characteristics of euchromatin?
Not stained during interphase
Central position in the nucleus
Promotes gene expression
Less compacted
Consider the regulation of the lac operon in E. coli. Which of the following is TRUE when the cell is in the presence of glucose but no lactose?
A) the repressor protein is not bound to the operator
B) CAP is not bound to the CAP site in the DNA
C) Adenylyl Cyclase is active
D) The operon is transcribed at high levels
E) All of the above
B) CAP is not bound to the CAP site in the DNA
Consider the regulation of the trp operon in E.coli. Transcription of the leader region has occurred, but there is no translation. Which of the following if TRUE?
A) The RNA polymerase will continue transcribing the operon
B) The repressor protein will block the RNA polymerase after the leader region
C) Region 1 of the leader region pairs with region 2 and region 3 pairs with region 4
D) Region 2 of the leader region pairs with region 3
C) Region 1 of the leader region pairs with region 2 and region 3 pairs with region 4
Which of the following is TRUE of DNA methylation in eukaryotes?
A) DNA methylation occurs at CpG
B) Methylation typically inhibits transcription by inhibiting initiation of transcription
C) de novo methylation is highly regulated
D) A and B
E) A, B and C
E) A, B and C
Which of the following is TRUE of epigenetic changes in gene expression?
A) Epigenetic changes can be heritable, meaning these changes can be passed to daughter cells following cell division
B) Epigenetic changes may involve changes in chromatin structure
C) Epigenetic changes result in a change in the DNA sequence
D) A and B
E) A, B and C
D) A and B
The maltose operon contains three genes: malE, malF, and malG. Transcription of this operon would result in ___ mRNA transcript(s) which encodes ___ stop codon(s).
1:3
Chapter 14
Slides 21-30
