AP BIOLOGY CHAPTER 15 MCQS Flashcards

The role of a metabolite that controls a repressible operon is to
A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
C) increase the production of inactive repressor proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it.

The tryptophan operon is a repressible operon that is
A) permanently turned on.
B) turned on only when tryptophan is present in the growth medium.
C) turned off only when glucose is present in the growth medium.
D) turned on only when glucose is present in the growth medium.
E) turned off whenever tryptophan is added to the growth medium.

Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor
E) corepressor

A lack of which molecule would result in the cell's inability to "turn off" genes?
A) operon
B) inducer
C) promoter
D) ubiquitin
E) corepressor

Which of the following, when taken up by the cell, binds to the repressor so that the repressor
no longer binds to the operator?
A) ubiquitin
B) inducer
C) promoter
D) repressor
E) corepressor

Most repressor proteins are allosteric. Which of the following binds with the repressor to alter
its conformation?
A) inducer
B) promoter
C) RNA polymerase
D) transcription factor
E) cAMP

A mutation that inactivates the 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) inactivation of RNA polymerase by alteration of its active site.
E) continuous translation of the mRNA because of alteration of its structure.

The lactose operon is likely to be transcribed when
A) there is more glucose in the cell than lactose.
B) the cyclic AMP levels are low.
C) there is glucose but no lactose in the cell.
D) the cyclic AMP and lactose levels are both high within the cell.
E) the cAMP level is high and the lactose level is low.

Transcription of the 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.
E) does not result in the production of enzymes.

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 cannot be present, and the repressor must be inactive.
E) RNA polymerase must not occupy the promoter, and the repressor must be inactive.

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is
presented for the first time with the sugar lactose (containing allolactose) as a potential food
source. Which of the following occurs when the lactose enters the cell?
A) The repressor protein attaches to the regulator.
B) Allolactose binds to the repressor protein.
C) Allolactose binds to the regulator gene.
D) The repressor protein and allolactose bind to RNA polymerase.
E) RNA polymerase attaches to the regulator.

Altering patterns of gene expression in prokaryotes would most likely serve the organism's
survival in which of the following ways?
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 the organism to adjust to changes in environmental conditions
D) allowing young organisms to respond differently from more mature organisms
E) allowing environmental changes to alter the prokaryote's genome

In response to chemical signals, prokaryotes can do which of the following?
A) turn off translation of their mRNA
B) alter the level of production of various enzymes
C) increase the number and responsiveness of their ribosomes
D) inactivate their mRNA molecules
E) alter the sequence of amino acids in certain proteins

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?
A) increase in glucose and increase in cAMP
B) decrease in glucose and increase in cAMP
C) increase in glucose and decrease in cAMP
D) decrease in glucose and increase in repressor
E) decrease in glucose and decrease in repressor

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 molecules that bind to one another.
E) It makes a repressor that binds CAP.

Which of the following mechanisms is used to coordinate the expression of multiple, related
genes in eukaryotic cells?
A) A specific combination of control elements in each gene’s enhancer coordinates the
simultaneous activation of the genes.
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 large operons, allowing them to be transcribed as a single unit.
D) A single repressor is able to turn off several related genes.
E) Environmental signals enter the cell and bind directly to promoters.

If you were to observe the activity of methylated DNA, you would expect it to
A) be replicating nearly continuously.
B) be unwinding in preparation for protein synthesis.
C) have turned off or slowed down the process of transcription.
D) be very actively transcribed and translated.
E) induce protein synthesis by not allowing repressors to bind to it.

Genomic imprinting, DNA methylation, and histone acetylation are all examples of
A) genetic mutation.
B) chromosomal rearrangements.
C) karyotypes.
D) epigenetic phenomena.
E) translocation.

When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to
interact with proteins required for gene expression. Therefore, to allow for these proteins to act,
the chromatin must constantly alter its structure. Which processes contribute to this dynamic
activity?
A) DNA supercoiling at or around H1
B) methylation and phosphorylation of histone tails
C) hydrolysis of DNA molecules where they are wrapped around the nucleosome core
D) accessibility of heterochromatin to phosphorylating enzymes
E) nucleotide excision and reconstruction

Two potential devices that eukaryotic cells use to regulate transcription are
A) DNA methylation and histone amplification.
B) DNA amplification and histone methylation.
C) DNA acetylation and methylation.
D) DNA methylation and histone modification.
E) histone amplification and DNA acetylation.

During DNA replication,
A) all methylation of the DNA is lost at the first round of replication.
B) DNA polymerase is blocked by methyl groups, and methylated regions of the genome are
therefore left uncopied.
C) methylation of the DNA is maintained because methylation enzymes act at DNA sites where
one strand is already methylated and thus correctly methylates daughter strands after replication.
D) methylation of the DNA is maintained because DNA polymerase directly incorporates
methylated nucleotides into the new strand opposite any methylated nucleotides in the template.
E) methylated DNA is copied in the cytoplasm, and unmethylated DNA is copied in the nucleus.

In eukaryotes, general transcription factors
A) are required for the expression of specific protein-encoding genes.
B) bind to other proteins or to a sequence element within the promoter called the TATA box.
C) inhibit RNA polymerase binding to the promoter and begin transcribing.
D) usually lead to a high level of transcription even without additional specific transcription
factors.
E) bind to sequences just after the start site of transcription.

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.
E) promoting the formation of looped domains in certain regions of DNA.

Transcription factors in eukaryotes usually have DNA binding domains as well as other
domains that are also specific for binding. In general, which of the following would you expect
many of them to be able to bind?
A) repressors
B) ATP
C) protein-based hormones
D) other transcription factors
E) tRNA

Gene expression might be altered at the level of post-transcriptional processing in eukaryotes
rather than prokaryotes because of which of the following?
A) Eukaryotic mRNAs get 5' caps and 3' tails.
B) Prokaryotic genes are expressed as mRNA, which is more stable in the cell.
C) Eukaryotic exons may be spliced in alternative patterns.
D) Prokaryotes use ribosomes of different structure and size.
E) Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.

Which of the following is most likely to have a small protein called ubiquitin attached to it?
A) a cyclin that usually acts in G1, now that the cell is in G2
B) a cell surface protein that requires transport from the ER
C) an mRNA that is leaving the nucleus to be translated
D) a regulatory protein that requires sugar residues to be attached
E) an mRNA produced by an egg cell that will be retained until after fertilization

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 targeting.
E) RNA disposal.

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. There was
surprise expressed by many that the number of protein-coding sequences was much smaller than
they had expected. Which of the following could account for most of the rest?
A) "junk" DNA that serves no possible purpose
B) rRNA and tRNA coding sequences
C) DNA that is translated directly without being transcribed
D) non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological
function
E) non-protein-coding DNA that is transcribed into several kinds of small RNAs without
biological function

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.
E) RNAi.

Which of the following best describes siRNA?
A) a short 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
E) a molecule, known as Dicer, that can degrade other mRNA sequences

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with
the possibilities for their use in medicine. Of the following scenarios for future research, which
would you expect to gain most from RNAs?
A) exploring a way to turn on the expression of pseudogenes
B) targeting siRNAs to disable the expression of an allele associated with autosomal recessive
disease
C) targeting siRNAs to disable the expression of an allele associated with autosomal dominant
disease
D) creating knock-out organisms that can be useful for pharmaceutical drug design
E) looking for a way to prevent viral DNA from causing infection in humans

Since Watson and Crick described DNA in 1953, which of the following might best explain
why the function of small RNAs is still being explained?
A) As RNAs have evolved since that time, they have taken on new functions.
B) Watson and Crick described DNA but did not predict any function for RNA.
C) The functions of small RNAs could not be approached until the entire human genome was
sequenced.
D) Ethical considerations prevented scientists from exploring this material until recently.
E) Changes in technology as well as our ability to determine how much of the DNA is expressed
have now made this possible.

You are given an experimental problem involving control of a gene's expression in the
embryo of a particular species. One of your first questions is whether the gene's expression is
controlled at the level of transcription or translation. Which of the following might best give you
an answer?
A) You explore whether there has been alternative splicing by examining amino acid sequences
of very similar proteins.
B) You measure the quantity of the appropriate pre-mRNA in various cell types and find they are
all the same.
C) You assess the position and sequence of the promoter and enhancer for this gene.
D) An analysis of amino acid production by the cell shows you that there is an increase at this
stage of embryonic life.
E) You use an antibiotic known to prevent translation.

In a genome-wide expression study using a DNA microarray assay, each well is used to
detect the
A) fate of proteins produced by a cell.
B) location of a protein produced by a cell.
C) location of a gene within a cell.
D) expression of a specific gene by a cell.
E) type of chemical modification of proteins produced by a cell.

DNA microarrays have had a huge impact on genomic studies because they
A) can identify the function of any gene in a genome.
B) can be used to introduce entire genomes into bacterial cells.
C) allow the expression of many or even all of the genes in a genome to be compared at once.
D) allow physical maps of the genome to be assembled in a very short time.
E) dramatically enhance the efficiency of restriction enzymes (endonucleases).

Researchers are looking for better treatments for breast cancer. For a particular DNA
microarray assay (DNA chip), cDNA has been made from the mRNAs of a dozen patients' breast
tumor biopsies. The researchers will be looking for a
A) particular gene that is amplified in all or most of the patient samples.
B) pattern of fluorescence that indicates which cells are overproliferating.
C) pattern shared among some or all of the samples that indicates gene expression differing from
control samples.
D) group of cDNAs that act differently from those on the rest of the grid.
E) group of cDNAs that match those in non-breast-cancer control samples from the same

Which one of the following techniques involves reverse transcriptase, PCR amplification,
and gel electrophoresis?
A) DNA microarray assays
B) RT-PCR
C) in situ hybridization
D) RNA interference
E) nucleic acid hybridization