chapter 18 Flashcards

1) Which of the following molecules is a protein produced by a regulatory gene? A) operator B) repressor C) operon D) promoter

2) Which of the following is a molecule that helps to "turn off" the expression of genes in a cell? A) inducer B) operator C) corepressor D) promoter

3)
When taken up by a cell, which of the following molecules binds to a repressor so that the repressor no longer
binds to an operator? A) inducer B) cAMP C) promoter D) corepressor

4)
Which of the following molecules binds with a repressor to alter its conformation and therefore affect its
function? A) transcription factor B) cAMP C) inducer D) promoter

5)
If a mutation deactivated a regulatory gene of a repressible operon in an E. coli cell which of the following
describes the most likely outcome? A) continuous translation of the mRNA because of alteration of its structure B) irreversible binding of the repressor to the operator C) continuous transcription of the structural gene controlled by that regulator D) complete inhibition of transcription of the structural gene controlled by that regulator

6) Which of the following conditions is most likely to result in transcription of the lac operon? A) There is glucose but no lactose in the cell. B) There is more glucose in the cell than lactose. C) The cAMP and lactose levels are both high within the cell. D) The cAMP level is high and the lactose level is low.

7) Which of the following predictions about the survival of a lactose intolerant E. coli cell is most likely correct? A) The cell will not survive because E. coli require lactose as a nutrient source for life. B) The cell will not survive because inducible operons must be stimulated for the cell to survive. C) The cell will survive if the cell has high levels of lacI expression. D) The cell will survive if the environment has sufficient glucose.

8) Under which condition do high levels of transcription of structural genes occur in an inducible operon? A) It stops when the pathway's product is present. B) It occurs continuously in the cell. C) It starts when the pathway's substrate is present. D) It starts when the pathway's product is present.

9) For a repressible operon to be transcribed, which of the following conditions must occur? A) RNA polymerase must bind to the promoter, and the repressor must be inactive. B) RNA polymerase must bind to the promoter and a corepressor must be present. C) RNA polymerase and active repressor must occupy the promoter. D) RNA polymerase must bind the inducer, and the repressor must be inactive.

10)
Prokaryote's ability to regulate patterns of gene expression most likely promotes the organism's survival by
________. A) allowing each gene to be expressed an equal number of times B) allowing environmental changes to alter a prokaryote's genome C) allowing an organism to adjust to changes in environmental conditions D) organizing gene expression, so that genes are expressed in a given order

11)
Which of the following changes in conditions results in an increase in cAMP receptor protein (CRP) mediated
initiation of transcription? A) an increase in glucose and a decrease in cAMP B) a decrease in glucose and a decrease in the repressor C) an increase in glucose and an increase in the repressor D) a decrease in glucose and an increase in cAMP

12)
A mutation in E. coli results in a molecule known as a "super-repressor" because the operon is permanently
repressed. Which of the following describes the most likely effect of the mutation on the repressor protein? A) It cannot make a functional repressor. B) It cannot bind to the operator. C) It cannot bind to the inducer. D) It makes a repressor that binds CAP.

13)
If a researcher 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 results would be most likely? A) Beta galactosidase will not be produced. B) The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be translated. C) RNA polymerase will no longer transcribe permease. D) The three genes of the lac operon will be expressed normally.

14)
If a researcher moves the operator to the far end of the operon, which of the following processes would likely
occur when the cell is exposed to lactose? A) The genes of the lac operon will be transcribed continuously. B) The inducer will no longer bind to the repressor. C) The operon will never be transcribed. D) The repressor will no longer bind to the operator.

15)
If a researcher moves the repressor gene (lacI) and its promoter, to a position at some several thousand base
pairs away from its normal position, which of the following describes the most likely effect on the lac operon? A) The repressor will no longer bind to the inducer. B) The lac operon will be expressed continuously. C) The lac operon will function normally. D) The repressor will no longer bind to the operator.

16)
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) Only lacZ would be transcribed. B) Only lacY would be transcribed. C) The lac operon would be transcribed continuously. D) Genes involved in glucose metabolism would not be transcribed.

17) Under what conditions does the trp repressor block transcription of the trp operon? A) when the repressor binds to tryptophan B) when the repressor is not bound to the operator C) when the repressor is not bound to RNA polymerase D) when the repressor binds to the inducer

8) How does breakdown of glucose inhibit transcription of the lac operon? A) by weakening the binding of the repressor to the operator B) by strengthening the binding of the repressor to the operator C) by reducing the levels of intracellular cAMP D) by inhibiting RNA polymerase from opening the strands of DNA to initiate transcription

19) A rise in extracellular glucose results in which of the following changes at the lac operon? A) lac repressor is allosterically inactivated B) cAMP receptor protein (CRP) detaches from the lac promoter C) lac operator binds inducer with greater affinity D) RNA polymerase binds the lac promoter with greater affinity

20)
The cAMP receptor protein (CRP) is said to be responsible for positive regulation of the lac operon because
________. A) CRP prevents binding of the repressor to the operator B) CRP bound to the CRP-binding site stimulates the transcription of the lac operon C) CRP promotes the production of allolactose D) CRP levels rise when lactose is present in the environment

49)
In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the
following kinds of genes would you expect to be mutated? A) genes involved in control of the cell cycle B) genes regulating cell division in colon bacteria C) genes coding enzymes that act in the colon D) genes that are especially susceptible to mutation

50) Which of the following types of mutation would convert a proto-oncogene into an oncogene? A) a mutation that blocks transcription of the proto-oncogene B) a mutation that greatly increases the amount of the proto-oncogene protein C) a mutation that greatly reduces the stability of a proto-oncogene mRNA D) a deletion of most of the proto-oncogene coding sequence

51)
Which of the following describes the role typical proto-oncogenes have when they are expressed in cells that
are not cancerous? A) They suppress tumor growth. B) They inhibit differentiation. C) They enhance signaling from growth factor receptors. D) They stimulate normal cell growth and division.

52) Which of the following describes the normal function of the p53 gene product? A) It slows down the rate of DNA replication by interfering with the binding of DNA polymerase. B) It causes cells to reduce expression of genes involved in DNA repair. C) It inhibits the cell cycle. D) It allows cells to pass on mutations due to DNA damage.

53) Which of the following statements correctly describes a characteristic of tumor-suppressor genes? A) They encode proteins that help prevent uncontrolled cell growth. B) They often encode proteins that stimulate the cell cycle. C) They are cancer-causing genes introduced into cells by viruses. D) They are frequently overexpressed in cancerous cells.

54) Which of the following characterizes BRCA1 and BRCA2 as tumor-suppressor genes? A) Their normal products participate in repair of DNA damage. B) The normal genes code for estrogen receptors. C) The mutant forms of either one of these prevent breast cancer. D) They block penetration of breast cells by chemical carcinogens.

55) Forms of the Ras protein found in tumors usually cause which of the following events to occur? A) cell division to cease B) excessive cell division C) decreased cell-to-cell adhesion D) DNA replication to stop

56)
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which
type(s) of cancer? A) colorectal only B) lung only C) lung and prostate D) lung and breast

57)
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon,
then ________. A) the repressor is active in the absence of the amino acid B) the amino acid turns on transcription of the operon C) the amino acid inactivates the repressor D) the amino acid acts as a corepressor

58) Muscle cells differ from nerve cells mainly because they ________. A) contain different genes B) have unique ribosomes C) use different genetic codes D) express different genes

21)
Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant
to acetylation? A) The mutant will show decreased levels of gene expression. B) The mutant will show increased levels of gene expression. C) The mutant will grow rapidly. D) The mutant will require galactose for growth.

22)
Which of the following statements correctly describes the primary difference between enhancers and proximal
control elements? A) Enhancers improve transcription; proximal control elements inhibit transcription. B)
Enhancers are located considerable distances from the promoter; proximal control elements are close to
the promoter. C) Enhancers are transcription factors; proximal control elements are DNA sequences. D)
Enhancers are long regions of DNA; proximal control elements are shorter RNA molecules that stand in
for DNA.

23)
Which of the following best explains why a neuron and a pancreatic cell isolated from the same individual
contain different sets of proteins? A) Each cell type needs different proteins and, therefore, they break down proteins they don't need. B)
The genes in each cell type have different promoters and, therefore, they respond to different regulatory
proteins. C) Each cell type contains different regulatory proteins and, therefore, they express different proteins. D) The set of genes in each cell type are different, therefore, they express different proteins.

24)
Gene expression is often assayed by measuring the level of mRNA produced from a gene. Which of the
following levels of the control of gene expression can by analyzed by this type of assay? A) alternative splicing B) transcriptional control C) translational control D) replication control

25) Assays analyzing transcriptional control of gene expression focus on which of the following characteristics? A) size of the gene's open reading frame B) amount of the mRNA generated C) relative level of the protein produced D) number of copies of the gene in the organism

26)
Which of the following processes is the best way to determine whether alternative splicing of a given gene
occurs? A) Isolate the primary transcripts made from the given gene and compare the sequences. B) Isolate mRNA from the given gene and compare the sequences. C) Compare the sequences of the given gene and a gene known to undergo alternative splicing. D) Compare the size of the DNA within the given gene and a similar gene in a related organism.

27)
Which of the following mechanisms is commonly used to coordinate the expression of multiple, related genes in
eukaryotic cells? A) Environmental signals entering the cell cause the genes to rearrange into related sets. B) Groups of genes that are expressed together have specific combinations of control elements. C) Release of each gene's individual inducing molecule must be coordinated to coordinate gene expression. D) Related genes are organized in operons that share a promoter that controls their expression.

28) DNA methylation and histone acetylation are examples of which of the following processes? A) epigenetic phenomena B) translocation C) genetic mutation D) chromosomal rearrangements

29) Which of the following functions are characteristic of general transcription factors in eukaryotes? A) They are sufficient to allow high levels of transcription. B) They bind to other proteins or to the TATA box. C) They inhibit RNA polymerase binding to the promoter and begin transcribing. D) They bind to sequences just after the start site of transcription.

30) Which of the following describes how steroid hormones regulate gene expression? A) They activate translation of certain mRNAs. B) They bind to intracellular receptors and alter transcription of specific genes. C) They promote the degradation of specific mRNAs. D) They bind to control elements in a regulatory gene and promote synthesis of that operon.

31)
Which of the following characteristics of gene expression allows bacteria to quickly change protein synthesis
patterns in response to environmental changes? A) mRNA have long lifespans, allowing the bacteria to use them many times for translation. B) mRNAs that are produced are short-lived and degraded within a few minutes of being synthesized. C) mRNA is stored for later use when it is needed later. D) Operons are activated in the presence of transcription factors.

32)
Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic
cells is increased? A) decreased binding of transcription factors B) inactivation of the selected genes C) decreased chromatin condensation D) increased chromatin condensation

33)
If the DNA of a mammalian promoter region experiences increased methylation on cytosine (C) which of the
following results is most likely to occur? A) inactivation of the gene B) higher levels of transcription of certain genes C) activation of histone tails for enzymatic function D) decreased chromatin condensation

34) Which of the following methods are used by eukaryotes to control gene expression but are not used by bacteria? A) control of both RNA splicing and chromatin remodeling B) limiting access to free nucleic acids C) regulatory proteins binding to promoter sequences and determining polymerase used D) organization of genes in operons

35)
Which of the following processes destroys RNA molecules if they have a sequence complementary to an
introduced double-stranded RNA? A) RNA disposal B) RNA interference C) RNA obstruction D) RNA blocking

36)
Much of the human genome does not code for proteins. Which of the following types of DNA are found in these
regions of the genome? A) DNA that serves as binding sites for reverse transcriptase B) DNA that consists only of histone coding sequences C) DNA that is translated directly without being transcribed D) DNA that is transcribed into several kinds of small RNAs with biological function

37)
Which of the following types of RNA is responsible for helping to reestablish methylation patterns during
gamete formation? A) lncRNA B) piRNA C) miRNA D) siRNA

38) Which of the following statements best describes the characteristics of siRNA? A) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA B) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor C) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits D)
a single-stranded RNA that can fold into cloverleaf patterns due to regions of internal complementary
base pairs

39)
A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a
fluorescent probe to follow it. She found that the introduced strands separated; one strand degraded and the
other single-stranded RNA remained. The remaining strand is able to do which of the following? A) activate other siRNAs in the cell B) act as a template for transcription C) attach to histones in the chromatin D) bind to complementary regions of target mRNAs

40)
A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a
fluorescent probe to follow it. Later she finds that the introduced strands separate into single-stranded RNAs
and she hypothesizes that the molecules is acting as an miRNA. Which of the following pieces of evidence
would support her claim? A) After separating the strands she introduced shut down all translation. B) The amount of the RNA she introduced increases due to transcription. C) The rate of accumulation of the polypeptide encoded by the target mRNA is reduced. D) The degradation rate of the single strand is slower than that of other cellular mRNA's.

41) Which of the following conclusions is consistent with the fact that plants can be cloned from somatic cells? A) Differentiation does not occur in plants. B) Differentiation results in the loss of non-expressed genes. C) The differentiated state is normally very unstable. D) Differentiated cells retain all the genes of the zygote.

42)
Which of the following explains why introducing the MyoD protein into a fat cell causes that cell to become a
muscle cell but adding it to a neuron will have no effect? A) Muscle-specific gene expression requires a protein that neurons do not make. B) MyoD is causes positive feedback of MyoD expression in fats cells but not neurons. C) Neurons are a differentiation step after muscle cells, they cannot go "backwards." D) Fat cells are undifferentiated, the MyoD protein causes them to differentiate.

) Cytoplasmic determinants are best described as having which of the following characteristics? A)
They are single-stranded RNA molecules capable of binding complementary sequences and altering
translation. B) They are centromeric regions of DNA loosened for chromosomal replication by transcription factors. C) They are maternal substances in the egg that influence the course of early development. D) They are tissue-specific transcription factors expressed in the early embryo.

44)
The product of the bicoid gene in Drosophila is responsible for determining which of the following embryonic
features or structures during development? A) orientation of the anterior-posterior axis B) segmentation of developing limbs C) orientation of the left-right axis D) orientation of the dorsal-ventral axis

45)
If a mutation alters a maternal effect gene in a female Drosophila zygote, which of the following is most likely to
occur? A) Only her male offspring will show the mutant phenotype. B) She will not develop past the early embryonic stage. C) Only her female offspring will show the mutant phenotype. D) All of her offspring will show the mutant phenotype, regardless of their genotype

46) Mutations in which of the following genes result in transformations in the identity of entire body parts? A) segmentation genes B) inducers C) homeotic genes D) egg-polarity genes

47)
In wildtype Drosophila embryos, the bicoid mRNA is localized to the anterior end of the embryo. If bicoid mRNA
was injected into the embryo's posterior end as well, which of the following developmental events would
occur? A) The embryo would have altered segmentation. B) The embryo would grow extra wings and legs. C) The embryo would develop normally. D) The embryo would show anterior structures at both ends of the embryo.

48) A cell is considered to be differentiated if it has which of the following characteristics? A) The cell appears to be different from the surrounding cells. B) The cell replicates by the process of mitosis. C) The cell loses connections to the surrounding cells. D) The cell produces proteins specific to a particular cell type.

59) The functioning of enhancers is an example of ________. A) the stimulation of translation by initiation factors B) transcriptional control of gene expression C) post-translational control that activates certain proteins D) a eukaryotic equivalent of prokaryotic promoter functioning

60) Cell differentiation always involves ________. A) the movement of cells B) the selective loss of certain genes from the genome C) transcription of the myoD gene D) the production of tissue-specific proteins

61) Which of the following is an example of post-transcriptional control of gene expression? A) the removal of introns and alternative splicing of exons B) the addition of methyl groups to cytosine bases of DNA C) the binding of transcription factors to a promoter D) gene amplification contributing to cancer

62) What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? A) buildup of a substrate for the pathway controlled by the operon B) reduced transcription of the operon's genes C) irreversible binding of the repressor to the promoter D) continuous transcription of the operon's genes

)
Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and
mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene ________. A) normally leads to formation of tail structures B) is a protein present in all head structures C) normally leads to formation of head structures D) is transcribed in the early embryo

64) Which of the following statements about the DNA in one of your brain cells is true? A) Most of the DNA codes for protein. B) The majority of genes are likely to be transcribed. C) Each gene lies immediately adjacent to an enhancer. D) It is the same as the DNA in one of your liver cells.

65)
Within a cell, the amount of protein made using a given mRNA molecule in that cell depends partly on
________. A) the degree of DNA methylation B) the number of introns present in the mRNA C) the rate at which the mRNA is degraded D) the types of ribosomes present in the cytoplasm

66)
Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the
presence of these potential time bombs in eukaryotic cells? A) Proto-oncogenes first arose from viral infections. B) Proto-oncogenes are genetic "junk." C) Proto-oncogenes are mutant versions of normal genes. D) Proto-oncogenes normally help regulate cell division.