Chapter 18

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1

1) Which of the following is a protein produced by a regulatory gene?

A) operon
B) inducer
C) promoter

D) repressor

Answer: D

2

2) A lack of which molecule would result in a cell's inability to "turn off" genes?

A) operon
B) inducer
C) promoter

D) corepressor

Answer: D

3

3) 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

Answer: A

4

4) 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

Answer: A

5

5) 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

Answer: A

6

6) 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

Answer: C

7

7) 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

Answer: B

8

8) 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.

Answer: C

9

9) 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

Answer: C

10

10) 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

Answer: B

11

11) 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.

Answer: C

12

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.

Answer: D

13

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.

13) 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.

Answer: D

14

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.

14) 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

Answer: D

15

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.

15) 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)

Answer: C

16

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.

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) 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.

Answer: A

17

7) 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

Answer: B

18

18) 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

Answer: D

19

19) 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

Answer: D

20

20) 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.

Answer: C

21

21) 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

Answer: C

22

22) 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

Answer: C

23

23) 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

Answer: D

24

24) 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

Answer: C

25

25) 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

Answer: D

26

26) 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.

Answer: B

27

27) DNA methylation and histone acetylation are examples of _____.

A) genetic mutation
B) chromosomal rearrangements
C) epigenetic phenomena

D) translocation

Answer: C

28

28) 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

Answer: A

29

29) 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

Answer: D

30

30) 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

Answer: A

31

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.

31) 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

Answer: B

32

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.

32) 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

Answer: D

33

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.

33) 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

Answer: D

34

34) 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

Answer: A

35

35) 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

Answer: C

36

36) 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

Answer: B

37

37) 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

Answer: A

38

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

Answer: B

39

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.

Answer: B

40

40) The fact that plants can be cloned from somatic cells demonstrates that _____.

A) differentiated cells retain all the genes of the zygote
B) genes are lost during differentiation
C) the differentiated state is normally very unstable

D) differentiation does not occur in plants

Answer: A

41

41) Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
A) morphogenesis

B) determination
C) differentiation
D) pattern formation

Answer: D

42

42) The product of the bicoid gene in Drosophila provides essential information about _____.

A) the dorsal-ventral axis
B) the left-right axis
C) segmentation

D) the anterior-posterior axis

Answer: D

43

43) If a Drosophila female has a homozygous mutation for a maternal effect gene, _____.

A) she will not develop past the early embryonic stage
B) all of her offspring will show the mutant phenotype, regardless of their genotype
C) only her male offspring will show the mutant phenotype

D) only her female offspring will show the mutant phenotype

Answer: B

44

44) Mutations in which of the following genes lead to transformations in the identity of entire body parts?
A) segmentation genes
B) egg-polarity genes

C) homeotic genes
D) inducers

Answer: C

45

45) Which of the following are maternal effect genes that control the orientation of the egg and thus the Drosophila embryo?
A) homeotic genes
B) segmentation genes

C) egg-polarity genes
D) morphogens

Answer: C

46

46) The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?
A) The embryo would grow extra wings and legs.

B) The embryo would probably show no anterior development and die.

C) Anterior structures would form in both ends of the embryo.
D) The embryo would develop normally.

Answer: C

47

47) 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 coding for enzymes that act in the colon
B) genes involved in control of the cell cycle

C) genes that are especially susceptible to mutation
D) genes of the bacteria, which are abundant in the colon

Answer: B

48

48) A cell is considered to be differentiated when it _____.

A) replicates by the process of mitosis
B) loses connections to the surrounding cells
C) produces proteins specific to a particular cell type

D) appears to be different from the surrounding cells

Answer: C

49

49) When the Bicoid protein is expressed in Drosophila, the embryo is still syncytial (divisions between cells are not yet fully developed). This information helps to explain which observation by Nüsslein-Volhard and Wieschaus?
A) mRNA from the egg is translated into the Bicoid protein.

B) Bicoid protein diffuses throughout the embryo in a concentration gradient.

C) Bicoid protein serves as a transcription regulator.
D) Bicoid protein determines the dorsoventral axis of the embryo.

Answer: B

50

50) The protein of the bicoid gene in Drosophila determines the _____ of the embryo.

A) anterior-posterior axis
B) anterior-lateral axis
C) posterior-dorsal axis

D) posterior-ventral axis

Answer: A

51

51) 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 creates an unstable proto-oncogene mRNA
C) a mutation that greatly increases the amount of the proto-oncogene protein

D) a deletion of most of the proto-oncogene coding sequence

Answer: C

52

52) Proto-oncogenes _____.
A) normally suppress tumor growth
B) are produced by somatic mutations induced by carcinogenic substances

C) stimulate normal cell growth and division
D) are underexpressed in cancer cells

Answer: C

53

53) The product of the p53 gene _____.
A) inhibits the cell cycle
B) slows down the rate of DNA replication by interfering with the binding of DNA polymerase C) causes cells to reduce expression of genes involved in DNA repair
D) allows cells to pass on mutations due to DNA damage

Answer: A

54

54) Tumor-suppressor genes _____.
A) are frequently overexpressed in cancerous cells
B) are cancer-causing genes introduced into cells by viruses

C) encode proteins that help prevent uncontrolled cell growth

D) often encode proteins that stimulate the cell cycle

Answer: C

55

55) BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.

A) their normal products participate in repair of DNA damage
B) the mutant forms of either one of these prevent breast cancer
C) the normal genes make estrogen receptors

D) they block penetration of breast cells by chemical carcinogens

Answer: A

56

56) Forms of the Ras protein found in tumors usually cause which of the following?

A) DNA replication to stop
B) cell-to-cell adhesion to be nonfunctional
C) cell division to cease

D) excessive cell division

Answer: D

57

57) 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 and breast

C) lung only
D) lung and prostate

Answer: A

58

58) 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 coding for enzymes that act in the colon
B) genes involved in control of the cell cycle

C) genes that are especially susceptible to mutation
D) genes of the bacteria, which are abundant in the colon

Answer: B