Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor
D
A lack of which molecule would result in a cell's inability to "turn off" genes?
A) operon
B) inducer
C) promoter
D) corepressor
D
Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?
A) inducer
B) promoter
C) repressor
D) corepressor
A
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?
A) inducer
B) promoter
C) transcription factor
D) cAMP
A
A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____.
A) continuous transcription of the structural gene controlled by that regulator
B) complete inhibition of transcription of the structural gene controlled by that regulator
C) irreversible binding of the repressor to the operator
D) continuous translation of the mRNA because of alteration of its structure
A
The lactose operon is likely to be transcribed when _____.
A) there is more glucose in the cell than lactose
B) there is glucose but no lactose in the cell
C) the cyclic AMP and lactose levels are both high within the cell
D) the cAMP level is high and the lactose level is low
C
Transcription of structural genes in an inducible operon _____.
A) occurs continuously in the cell
B) starts when the pathway's substrate is present
C) starts when the pathway's product is present
D) stops when the pathway's product is present
B
For a repressible operon to be transcribed, which of the following must occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase must not occupy the promoter, and the repressor must be inactive.
C
Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____.
A) organizing gene expression, so that genes are expressed in a given order
B) allowing each gene to be expressed an equal number of times
C) allowing an organism to adjust to changes in environmental conditions
D) allowing environmental changes to alter a prokaryote's genome
C
In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP activity in stimulating transcription?
A) an increase in glucose and an increase in cAMP
B) a decrease in glucose and an increase in cAMP
C) an increase in glucose and a decrease in cAMP
D) a decrease in glucose and a decrease in the repressor
B
There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?
A) It cannot bind to the operator.
B) It cannot make a functional repressor.
C) It cannot bind to the inducer.
D) It makes a repressor that binds CAP.
C
Use this information to answer the question(s) below.
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.
12) If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?
A) The three structural genes will be expressed normally.
B) RNA polymerase will no longer transcribe permease.
C) The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be translated.
D) Beta galactosidase will not be produced.
D
If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following would likely occur when the cell is exposed to lactose?
A) The inducer will no longer bind to the repressor.
B) The repressor will no longer bind to the operator.
C) The operon will never be transcribed.
D) The structural genes will be transcribed continuously.
D
If she moves the repressor gene (lacI), along with its promoter, to a position at some several thousand base pairs away from its normal position, we would expect the _____.
A) repressor will no longer bind to the operator
B) repressor will no longer bind to the inducer
C) lac operon will be expressed continuously
D) lac operon will function normally
D
What would occur if the repressor of an inducible operon were mutated so that it could not bind the operator?
A) irreversible binding of the repressor to the promoter
B) reduced transcription of the operon's genes
C) continuous transcription of the operon's genes
D) overproduction of catabolite activator protein (CAP)
C
According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?
A) The lac operon would be transcribed continuously.
B) Only lacZ would be transcribed.
C) Only lacY would be transcribed.
D) Galactosidase permease would be produced, but would be incapable of transporting lactose.
A
The trp repressor blocks transcription of the trp operon when the repressor _____.
A) binds to the inducer
B) binds to tryptophan
C) is not bound to tryptophan
D) is not bound to the operator
B
Extracellular glucose inhibits transcription of the lac operon by _____.
A) strengthening the binding of the repressor to the operator
B) weakening the binding of the repressor to the operator
C) inhibiting RNA polymerase from opening the strands of DNA to initiate transcription
D) reducing the levels of intracellular cAMP
D
CAP is said to be responsible for positive regulation of the lac operon because _____.
- A) CAP binds cAMP
- B) CAP binds to the CAP-binding site
- C) CAP prevents binding of the repressor to the operator
- D) CAP bound to the CAP-binding site increases the frequency of transcription initiation
D
Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
A) The mutant will grow rapidly.
B) The mutant will require galactose for growth.
C) The mutant will show low levels of gene expression.
D) The mutant will show high levels of gene expression.
C
The primary difference between enhancers and promoter-proximal elements is that enhancers _____.
A) are transcription factors; promoter-proximal elements are DNA sequences
B) enhance transcription; promoter-proximal elements inhibit transcription
C) are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
D) are DNA sequences; promoter-proximal elements are proteins
C
The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.
A) genes
B) regulatory sequences
C) sets of regulatory proteins
D) promoters
C
Gene expression is often assayed by measuring the level of mRNA produced from a gene. If one is interested in knowing the amount of a final active gene product, a potential problem of this method is that it ignores the possibility of _____.
A) chromatin condensation control
B) transcriptional control
C) alternative splicing
D) translational control
D
Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread _____.
A) chromatin condensation control
B) transcriptional control
C) alternative splicing
D) translational control
C
One way to detect alternative splicing of transcripts from a given gene is to _____.
A) compare the DNA sequence of the given gene to that of a similar gene in a related organism
B) measure the relative rates of transcription of the given gene compared to that of a gene known to be constitutively spliced
C) compare the sequences of different primary transcripts made from the given gene
D) compare the sequences of different mRNAs made from the given gene
D
Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
A) Environmental signals enter the cell and bind directly to promoters.
B) The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time.
C) The genes are organized into a large operon, allowing them to be coordinately controlled as a single unit.
D) A single repressor is able to turn off several related genes.
B
DNA methylation and histone acetylation are examples of _____.
- A) genetic mutation
- B) chromosomal rearrangements
- C) epigenetic phenomena
- D) translocation
C
In eukaryotes, general transcription factors _____
A) bind to other proteins or to the TATA box
B) inhibit RNA polymerase binding to the promoter and begin transcribing
C) usually lead to a high level of transcription even without additional specific transcription factors
D) bind to sequences just after the start site of transcription
A
Steroid hormones produce their effects in cells by _____.
A) activating key enzymes in metabolic pathways
B) activating translation of certain mRNAs
C) promoting the degradation of specific mRNAs
D) binding to intracellular receptors and promoting transcription of specific genes
D
Which of the following is most likely to have a small protein called ubiquitin attached to it?
- A) a cyclin protein, that usually acts in G1, in a cell that is in G2
- B) a cell surface protein that requires transport from the ER
- C) an mRNA leaving the nucleus to be translated
- D) an mRNA produced by an egg cell that will be retained until after fertilization
A
Use this information to answer the question(s) below.
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.
In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?
- A) increased chromatin condensation
- B) decreased chromatin condensation
- C) decreased binding of transcription factors
- D) inactivation of the selected genes
B
One of her colleagues suggested she try increased methylation of C nucleotides in the DNA of promoters of a mammalian system. Which of the following results would she most likely see?
A) decreased chromatin condensation
B) activation of histone tails for enzymatic function
C) higher levels of transcription of certain genes
D) inactivation of the selected genes
D
Which method is utilized by eukaryotes to control their gene expression that is NOT used in bacteria?
A) control of chromatin remodeling
B) control of RNA splicing
C) transcriptional control
D) control of both RNA splicing and chromatin remodeling
D
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called _____.
A) RNA interference
B) RNA obstruction
C) RNA blocking
D) RNA disposal
A
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is not coding for proteins?
A) DNA that consists of histone coding sequences
B) DNA that is translated directly without being transcribed
C) non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
D) non-protein-coding DNA that serves as binding sites for reverse transcriptase
C
Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. These are known as _____.
A) miRNA
B) piRNA
C) snRNA
D) siRNA
B
Which of the following best describes siRNA?
A) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
B) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns
C) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
D) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
A
A researcher introduces double-stranded RNA into a culture of mammalian cells and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe.
38) Some time later, she finds that the introduced strand separates into single-stranded RNAs, one of which is degraded. What does this enable the remaining strand to do?
A) attach to histones in the chromatin
B) bind to complementary regions of target mRNAs
C) activate other siRNAs in the cell
D) bind to noncomplementary RNA sequences
B
A researcher introduces double-stranded RNA into a culture of mammalian cells and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe.
39) When she finds that the introduced strand separates into single-stranded RNAs, what other evidence of this single-stranded RNA piece's activity can she find?
A) She can measure the degradation rate of the remaining single strand.
B) The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
C) The amount of miRNA is multiplied by its replication.
D) The cell's translation ability is entirely shut down.
B