AP Bio: Chapter 15
Which of these is NOT a component of the lac operon? 1. lactose-utilization genes only 2. promoter only 3. regulatory gene only 4. operator only 5. promoter and operator
regulatory gene only
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the repressor gene (lac I), along with its promoter, to a position some several thousand base pairs away from its normal position, which will you expect to occur? 1. The repressor will no longer bind to the operator. 2. The repressor will no longer be made. 3. The repressor will no longer bind to the inducer. 4. The lac operon will be expressed continuously. 5. The lac operon will function normally.
The lac operon will function normally.
Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells? 1. A specific combination of control elements in each genes enhancer coordinates the simultaneous activation of the genes. 2. The genes are organized into large operons, allowing them to be transcribed as a single unit. 3. The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time. 4. Environmental signals enter the cell and bind directly to promoters. 5. A single repressor is able to turn off several related genes.
A specific combination of control elements in each genes enhancer coordinates the simultaneous activation of the genes.
_____ bind(s) to DNA enhancer regions. 1. RNA polymerase 2. Promoters 3. Introns 4. Activators 5. Exons
Activators
How are genes coordinately controlled in eukaryotic cells? 1. Coordinately controlled genes in eukaryotic cells are activated by the same chemical signals. 2. Coordinately controlled genes in eukaryotic cells share a set of control elements. 3. Coordinately controlled genes in eukaryotic cells are located together on the same chromosome.
Coordinately controlled genes in eukaryotic cells are activated by the same chemical signals AND Coordinately controlled genes in eukaryotic cells share a set of control elements.
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? 1. It cannot bind to the inducer. 2. It cannot make a functional repressor. 3. It makes a repressor that binds CAP. 4. It makes molecules that bind to one another. 5. It cannot bind to the operator.
It cannot bind to the inducer
Which of the following statements about the DNA in one of your brain cells is true? 1. The majority of genes are likely to be transcribed. 2. Each gene lies immediately adjacent to an enhancer. 3. Most of the DNA codes for protein. 4. It is the same as the DNA in one of your kidney cells. 5. Many genes are grouped into operon-like clusters.
It is the same as the DNA in one of your kidney cells.
Which of the following would not be true of cDNA produced using human brain tissue as the starting material? 1. It could be used as a probe to detect genes expressed in the brain. 2. It could be amplified by the polymerase chain reaction. 3. It would contain sequences representing all the genes in the genome. 4. It was produced from mRNA using reverse transcriptase. 5. It lacks the introns of the human genes.
It would contain sequences representing all the genes in the genome.
The operon model of the regulation of gene expression in bacteria was proposed by _____. 1. Watson and Crick 2. Franklin 3. Darwin 4. Jacob and Monod 5. Mendel
Jacob and Monod
For a repressible operon to be transcribed, which of the following must occur? 1. RNA polymerase must bind to the promoter, and the repressor must be inactive. 2. A corepressor must be present. 3. RNA polymerase must not occupy the promoter, and the repressor must be inactive. 4. RNA polymerase and the active repressor must be present. 5. RNA polymerase cannot be present, and the repressor must be inactive.
RNA polymerase must bind to the promoter, and the repressor must be inactive.
Which statement(s) about repressible operons is/are correct? 1. Repressible enzymes generally function in anabolic pathways. 2. A repressible operon is on unless a corepressor is present. 3. In a repressible operon, the repressor is synthesized in an active form.
Repressible enzymes generally function in anabolic pathways AND a repressible operon is on unless a corepressor is present.
The vertebrate Pax-6 gene product (the PAX-6 protein) triggers a complex program of gene expression resulting in formation of the vertebrate eye, which has a single lens. The fly Pax-6 gene leads to formation of the compound fly eye. When scientists cloned a mouse Pax-6 gene and introduced it into a fly embryo, it led to formation of the compound eye of a fly. What did scientists induce from this? 1. All genes controlling eye development are identical in flies and mice. 2. The Pax-6 genes of flies and mice arose from an ancestral gene in a common ancestor. 3. Flies and mice have a more recent common ancestor than we originally thought.
The Pax-6 genes of flies and mice arose from an ancestral gene in a common ancestor.
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Which of the following is a likely explanation for the lack of transgene expression in the fifth cell line? 1. The transgene integrated into a region of the genome characterized by high histone acetylation. 2. The transgene integrated into a euchromatic region of the genome. 3. The host cell lacks the enzymes necessary to express the transgene. 4. The transgene was mutated during the process of integration into the host cell genome. 5. The transgene integrated into a heterochromatic region of the genome.
The transgene integrated into a heterochromatic region of the genome.
A gene on human chromosome 15 is expressed throughout the body. However, in the brain, only the maternal copy of the gene is expressed, whereas the paternal copy of the gene is silent and not transcribed. What accounts for this pattern of expression this gene displays in the brain? 1. In the brain, the maternal copy of the gene is methylated whereas the paternal copy is un-methylated. 2. The copies of this gene in brain cells are coordinately controlled with the copies of the gene in body cells. 3. Through genomic imprinting, methylation regulates expression of the paternal copy of the gene in the brain.
Through genomic imprinting, methylation regulates expression of the paternal copy of the gene in the brain.
Why is the lac operon said to be an inducible operon? 1. When activated, the lac operon induces the production of lactose-digesting enzymes. 2. When activated, the lac operon induces repression of gene expression. 3. When allolactose is present, it induces the inactivation of the lac repressor. 4. When allolactose is present, it induces repression of gene expression. 5. When allolactose is present, it induces the activation of the lac repressor.
When allolactose is present, it induces the inactivation of the lac repressor.
Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways? 1. allowing the organism to adjust to changes in environmental conditions 2. allowing young organisms to respond differently from more mature organisms 3. allowing each gene to be expressed an equal number of times 4. allowing environmental changes to alter the prokaryote's genome 5. organizing gene expression so that genes are expressed in a given order
allowing the organism to adjust to changes in environmental conditions
In response to chemical signals, prokaryotes can do which of the following? 1. increase the number and responsiveness of their ribosomes 2. alter the sequence of amino acids in certain proteins 3. turn off translation of their mRNA 4. alter the level of production of various enzymes 5. inactivate their mRNA molecules
alter the level of production of various enzymes
In eukaryotes, general transcription factors 1. inhibit RNA polymerase binding to the promoter and begin transcribing. 2. are required for the expression of specific protein-encoding genes. 3. bind to sequences just after the start site of transcription. 4. bind to other proteins or to a sequence element within the promoter called the TATA box. 5. usually lead to a high level of transcription even without additional specific transcription factors.
bind to other proteins or to a sequence element within the promoter called the TATA box.
Steroid hormones produce their effects in cells by 1. promoting the degradation of specific mRNAs. 2. activating key enzymes in metabolic pathways. 3. binding to intracellular receptors and promoting transcription of specific genes. 4. promoting the formation of looped domains in certain regions of DNA. 5. activating translation of certain mRNAs.
binding to intracellular receptors and promoting transcription of specific genes.
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? 1. buildup of a substrate for the pathway controlled by the operon 2. overproduction of catabolite activator protein (CAP) 3. continuous transcription of the operon's genes 4. irreversible binding of the repressor to the promoter 5. reduced transcription of the operon's genes
continuous transcription of the operon's genes
A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in 1. irreversible binding of the repressor to the operator. 2. continuous transcription of the structural gene controlled by that regulator. 3. inactivation of RNA polymerase by alteration of its active site. 4. continuous translation of the mRNA because of alteration of its structure. 5. complete inhibition of transcription of the structural gene controlled by that regulator.
continuous transcription of the structural gene controlled by that regulator.
A lack of which molecule would result in the cell's inability to "turn off" genes? 1. operon 2. ubiquitin 3. corepressor 4. promoter 5. inducer
corepressor
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? 1. increase in glucose and increase in cAMP 2. increase in glucose and decrease in cAMP 3. decrease in glucose and increase in cAMP 4. decrease in glucose and decrease in repressor 5. decrease in glucose and increase in repressor
decrease in glucose and increase in cAMP
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 decreasing methylation of histone tails. Which of the following results would she most likely see? 1. increased chromatin condensation 2. decreased chromatin condensation 3. activation of histone tails for enzymatic function 4. decreased binding of transcription factors 5. inactivation of the selected genes
decreased chromatin condensation
Genomic imprinting, DNA methylation, and histone acetylation are all examples of 1. genetic mutation. 2. translocation. 3. epigenetic phenomena. 4. karyotypes. 5. chromosomal rearrangements.
epigenetic phenomena.
If you were to observe the activity of methylated DNA, you would expect it to 1. induce protein synthesis by not allowing repressors to bind to it. 2. have turned off or slowed down the process of transcription. 3. be replicating nearly continuously. 4. be unwinding in preparation for protein synthesis. 5. be very actively transcribed and translated.
have turned off or slowed down the process of transcription.
In humans, the hormone testosterone enters cells and binds to specific proteins, which in turn bind to specific sites on the cells' DNA. These proteins probably act to do what? 1. help RNA polymerase transcribe certain genes 2. promote recombination 3. unwind the DNA so that its genes can be transcribed 4. alter the pattern of DNA splicing 5. cause mutations in the DNA
help RNA polymerase transcribe certain genes
Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator? 1. inducer 2. repressor 3. corepressor 4. promoter 5. ubiquitin
inducer
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Of the lines that express the transgene, one is transcribed but not translated. Which of the following is a likely explanation? 1. no promoter 2. missing transcription factor 3. no compatible ribosome 4. no AUG in any frame 5. high histone acetylation
no AUG in any frame
In the presence of a regulatory protein the lac operon is _____. 1. transcribed 2. not transcribed 3. transcribed at a faster than usual rate 4. is turned on 5. either transcribed or not transcribed
not transcribed
Which of the following is a protein produced by a regulatory gene? 1. repressor 2. promoter 3. corepressor 4. inducer 5. operon
repressor
Transcription of the structural genes in an inducible operon 1. stops when the pathway's product is present. 2. does not result in the production of enzymes. 3. starts when the pathway's product is present. 4. starts when the pathway's substrate is present. 5. occurs continuously in the cell.
starts when the pathway's substrate is present.
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then 1. the amino acid turns on transcription of the operon. 2. the enzymes produced are called inducible enzymes. 3. the amino acid inactivates the repressor. 4. the repressor is active in the absence of the amino acid. 5. the amino acid acts as a corepressor.
the amino acid acts as a corepressor.
Regulatory proteins bind to _____. 1. the operator 2. the lactose-utilization genes 3. the regulatory gene 4. RNA polymerase 5. transcription factors
the operator
Which of the following is an example of post-transcriptional control of gene expression? 1. the folding of DNA to form heterochromatin 2. the removal of introns and alternative splicing of exons 3. the binding of RNA polymerase to transcription factors 4. the binding of transcription factors to a promoter 5. the addition of methyl groups to cytosine bases of DNA
the removal of introns and alternative splicing of exons
The functioning of enhancers is an example of 1. a post-transcriptional mechanism to regulate mRNA. 2. post-translational control that activates certain proteins. 3. transcriptional control of gene expression. 4. the stimulation of translation by initiation factors. 5. a eukaryotic equivalent of prokaryotic promoter functioning.
transcriptional control of gene expression.
The tryptophan operon is a repressible operon that is 1. permanently turned on. 2. turned on only when tryptophan is present in the growth medium. 3. turned off only when glucose is present in the growth medium. 4. turned on only when glucose is present in the growth medium. 5. turned off whenever tryptophan is added to the growth medium.
turned off whenever tryptophan is added to the growth medium.
