Deck 12: Gene Regulation and Cancer

Question 1

Which of the following events in gene expression control does not occur in the nucleus?

A) chromatin condensation
B) mRNA translation
C) DNA transcription
D) mRNA processing
E) transcription factor binding

Answer 1

B
Explanation: All of the above processes, except for translation of mRNA, occur within the nucleus.

Question 2

In the absence of lactose,

A) the repressor binds to the operator, and the genes of the lac operon are transcribed.
B) the repressor binds to the operator, and the genes of the lac operon are not transcribed.
C) the repressor is unable to bind to the operator, and the genes of the lac operon are transcribed.
D) the repressor is unable to bind to the operator, and the genes of the lac operon are not transcribed.
E) the repressor is unable to bind to the operator, and the regulatory gene is transcribed.

Answer 2

B
Explanation: A regulatory gene encodes a repressor protein, which is transcribed and translated. The active repressor protein binds the operator (regulatory DNA sequence) of the lac operon, and transcription of the genes of the lac operon does not occur.

Question 3

Figure:
Which of the DNA sequences shown in the figure are transcribed and translated to produce proteins?

A) 1, 2, 3, and 4
B) 2 and 3
C) 2, 3, and 4
D) 1, 2, and 3
E) 1 and 4

Answer 3

E
Explanation: The promoter and operator sequences do not encode proteins. The DNA sequence of the operator serves as a binding site for the repressor protein, and the DNA sequence of the promoter serves as a binding site for RNA polymerase. Both are transcribed into mRNA, but these sequences do not encode protein and are not translated.

Question 4

Lactose ______ the repressor, causing it to ______.

A) inactivates; bind to the operator
B) inactivates; fail to bind to the operator
C) activates; bind to the operator
D) inactivates; bind to RNA polymerase
E) activates; bind to RNA polymerase

Question 5

Therapeutic cloning

A) can produce clones of adult individuals.
B) can be used to produce superior farm animals.
C) can produce specialized cells to treat human disease.
D) can be used to create new species of plants.
E) can produce embryonic stem cells.

Question 6

Transcription of the genes of the lac operon is ______ unless _______ is _______.

A) on; lactose; present
B) off; lactose; absent
C) off; repressor; absent
D) on; lactose; absent
E) off; lactose; present

Question 7

In prokaryotes, an operon includes

A) an operator and regulatory gene.
B) a repressor and promoter.
C) a cluster of genes and the DNA sequences that control their transcription.
D) RNA polymerase and the DNA sequences that control gene transcription.
E) regulatory genes that control the transcription of RNA polymerase.

Question 8

Prokaryotes cannot regulate gene expression at which of the following levels?

A) mRNA transcription and mRNA translation
B) mRNA translation
C) alternative mRNA processing and chromatin compaction
D) mRNA translation and longevity of mRNA
E) mRNA transcription and longevity of mRNA

Question 9

A(n) ___ is to reproductive cloning as a(n) ___ is to therapeutic cloning.

A) specialized cell; clone
B) clone; enucleated egg
C) clone; specialized cell
D) embryonic stem cell; adult stem cell
E) enucleated egg; specialized cell

Question 10

Cells from the root of a carrot may be used to generate an entire carrot plant. This illustrates that

A) only cells of the root contain the plant's genes.
B) every cell of the root contains all of the plant's genes.
C) plants are easier to clone than animals.
D) carrots may be used for therapeutic cloning.
E) a carrot's roots contain all of the tissues of an adult plant.

Question 11

Which of the following reasons explains a possible advantage of using adult stem cells in therapeutic cloning rather than embryonic stem cells?

A) Adult stem cells have a longer lifespan in culture than embryonic stem cells, and would persist for a longer time in the patient's body.
B) Embryonic stem cells would not be able to enter the correct tissue of the patient's body, unlike an adult stem cell.
C) Adult stem cells must be obtained from another individual before being injected into the patient, and would be less likely to be rejected by the patient's body.
D) Embryonic stem cells may stop dividing within the patient's body once injected, unlike adult stem cells.
E) Adult stem cells may be obtained from the patient and would be less likely to be rejected by the patient's body.

Question 12

In the regulation of the lac operon, when lactose is present,

A) lactose binds to the repressor, making it unable to bind to the operator and allowing transcription to proceed.
B) lactose binds to the operator, making the repressor unable to bind to the operator and allowing transcription to proceed.
C) the repressor binds to the operator, allowing transcription to proceed.
D) lactose binds to RNA polymerase, allowing transcription to proceed even in the presence of the repressor.
E) lactose binds to the repressor, causing it to bind to the operator and allowing transcription to proceed.

Question 13

Specialized cells differ from one another because

A) they only express certain genes.
B) they express all genes.
C) they turn off gene expression once specialized.
D) they may re-enter the cell cycle at any time.
E) they do not express housekeeping genes.

Question 14

In order to clone adult animals, scientists typically begin with

A) an isolated sperm cell.
B) an enucleated egg.
C) an enucleated liver cell.
D) a red blood cell.
E) an enucleated sperm cell.

Question 15

Figure:
Which of the DNA sequences shown in the figure is/are bound by a regulatory protein?

A) 1
B) 2
C) 3
D) 1 and 4
E) 2 and 3

Question 16

Transcription activators are different from transcription factors in that

A) transcription activators are required for RNA polymerase binding, while transcription factors slow RNA polymerase binding.
B) transcription activators accelerate transcription, while transcription factors assist RNA polymerase binding.
C) transcription activators slow transcription, while transcription factors accelerate transcription.
D) transcription factors prevent RNA polymerase binding, while transcription activators assist RNA polymerase binding.
E) transcription factors are required for RNA polymerase binding, while transcription activators accelerate transcription.

Question 17

Why is it necessary to "starve" the donor cells prior to reproductive cloning?

A) to force the cells into G₀ stage so that the nuclei removed from them will respond to cytoplasmic growth signals
B) to force the enucleated egg cell into G₀ stage so that it would accept the donor nucleus
C) to lengthen the telomeres in the donor nucleus
D) to make the nucleus "start over" in the S stage so that the nucleus will be diploid
E) to make the nucleus "start over" in the S stage so that the nucleus will be haploid

Question 18

Why do adult stem cells currently have fewer uses in therapeutic cloning than embryonic stem cells?

A) Embryonic stem cells have longer telomeres and persist for much longer than adult stem cells.
B) Embryonic stem cells are capable of reverting to a G₀ stage when starved.
C) Adult stem cells may become any type of cell, whereas embryonic stem cells may only become adult stem cells first.
D) Embryonic stem cells may become any type of cell, whereas adult stem cells may only become a limited number of cell types.
E) Adult stem cells have more restrictions that prevent them from re-entering the cell cycle at the G₀ stage.

Question 19

What would be the most likely result on the regulation of the lac operon from a non-functional repressor protein?

A) transcription of the lactose metabolizing genes, even when lactose is absent
B) no transcription of the lactose metabolizing genes, even when lactose is present
C) binding of the repressor protein to the operator even when lactose is present
D) binding of the repressor protein to the regulatory gene in both the presence and absence of lactose
E) no transcription of the regulatory gene, even in the presence of lactose

Question 20

A point mutation in the operator of the lac operon would most likely cause

A) no transcription of the lactose metabolizing genes, even when lactose is absent.
B) no transcription of the lactose metabolizing genes, even when lactose is present.
C) no binding of the repressor protein to the operator even when lactose is absent.
D) binding of the repressor protein to the regulatory gene in both the presence and absence of lactose.
E) no transcription of the regulatory gene, even in the presence of lactose.

Question 21

The protein derived from a particular gene is different when it is found in a neuron than in a muscle cell. This is most likely due to

A) alternative mRNA processing.
B) regulation of mRNA translation.
C) alteration of protein activity.
D) mRNA editing.
E) DNA excision.

Question 22

Inheritance of mutant forms of some genes may lead to a predisposition to develop cancer. Which of the genes listed below has not been linked to hereditary forms of cancer?

A) BRCA-1
B) RB
C) RET
D) ras
E) DScam

Question 23

A tumor suppressor gene undergoes a mutation that causes it to lose its normal function. What would be the most likely result of this mutation?

A) The cell cycle halts and reverses back to the G₀ stage.
B) The cell undergoes contact inhibition even when it is not surrounded by other cells.
C) The cell cycle accelerates.
D) The cell no longer responds to signals that cause it to stop dividing or undergo apoptosis.
E) The cell stops dividing permanently and will never re-enter the cell cycle.

Question 24

A proto-oncogene differs from a tumor suppressor gene because a proto-oncogene

A) may cause cancer if mutated, whereas a tumor suppressor gene cannot.
B) stimulates mitosis in a normal cell, whereas a tumor suppressor gene inhibits mitosis.
C) only activates enzymes in a cell that allow metastasis.
D) inhibits the cell cycle, whereas a tumor suppressor accelerates the cell cycle.
E) promotes meiosis, whereas a tumor suppressor gene promotes mitosis.

Question 25

If tumor cells have a faulty, non-functional proteinase, they will be unable to undergo which of the following processes?

A) mitosis
B) mutations
C) metastasis
D) apoptosis
E) angiogenesis

Question 26

The unpacking of heterochromatin into euchromatin does not immediately result in DNA transcription because

A) Barr bodies are still present.
B) histones still block the binding of RNA polymerase to the promoter.
C) euchromatin is always transcriptionally inactive.
D) transcription factors still block the binding of RNA polymerase to the promoter.
E) heterochromatin contains DNA with accessible promoters.

Question 27

A translocation may lead to cancer if it

A) disrupts control of expression of genes that regulate the cell cycle.
B) deletes the telomere of the chromosome.
C) moves genes from one chromosome to another.
D) activates tumor suppressor genes.
E) affects both tumor suppressor and proto-oncogenes.

Question 28

A woman inherits a mutant BRCA1 allele from her mother. She has an increased risk of developing breast cancer because

A) every cell in the woman's body has a copy of the mutant BRCA1 allele.
B) she still has one normal allele of the BRCA1 gene that can make up for the loss of function in the mutant allele.
C) some of the cells in her body are already cancerous, meaning that no further mutations are needed for a tumor to form.
D) the normal BRCA1 allele is more likely to mutate than in an individual without a mutant BRCA1 allele.
E) a mutation in her normal BRCA1 allele may lead to cancer, whereas a normal individual would have to acquire two mutations (one in each allele) to develop cancer.

Question 29

An oncogene is more likely to lead to cancer than a mutant tumor suppressor because

A) a gain of function mutation in an oncogene need only occur in one allele before it disrupts control of the cell cycle.
B) a loss of function mutation in an oncogene is sufficient to cause unregulated cell division.
C) the mutant oncogene may inactivate telomerase.
D) a gain of function mutation in a tumor suppressor gene can promote the cell cycle.
E) a gain of function mutation in an oncogene is more likely to cause the other allele to mutate.

Question 30

A protein that promotes apoptosis would be considered a(n)

A) oncogene.
B) proto-oncogene.
C) tumor suppressor.
D) mutant tumor suppressor.
E) signal transduction pathway protein.

Question 31

Female mammals form Barr bodies because

A) compacting the chromatin of one of their X chromosomes allows them to inactivate it and produce the same amount of gene product as a male.
B) unpacking one of their X chromosomes allows them to produce more gene product than a male.
C) compacting the chromatin in one of their X chromosomes allows them to conserve histone proteins.
D) compacting the chromatin in one of their X chromosomes allows them to produce more gene product than a male from the other X chromosome.
E) unpacking one of their X chromosomes allows them to choose which allele they wish to express, which a male cannot do.

Question 32

Which of the following series of events is in the correct order?

A) signal transduction pathway stimulates receptor, transcription activator is activated by target gene
B) chemical binds to receptor, signal transduction pathway stimulates transcription activator, target gene is transcribed and translated
C) chemical binds to receptor, target gene is transcribed and translated, signal transduction pathway stimulates proteins that bring about desired changes
D) signal transduction pathway activates receptor, chemical binds to receptor, target gene stimulates transcription activator
E) chemical binds to receptor, signal transduction pathway stimulates target gene, target gene stimulates transcription activator

Question 33

Heterochromatin differs from euchromatin in that heterochromatin

A) is transcriptionally active, whereas euchromatin is not.
B) is not found in Barr bodies.
C) is transcriptionally inactive.
D) is the result of the unpacking of euchromatin.
E) contains DNA with accessible promoters.

Question 34

Which of the following is not a characteristic of cancer cells?

A) stimulate the growth of blood vessels
B) travel through the bloodstream to other parts of the body
C) exhibit contact inhibition
D) have abnormal chromosomes
E) produced by a mutation of a proto-oncogene

Question 35

A mutation that causes a gain of function in a tumor suppressor gene would not likely cause cancer because a tumor suppressor protein

A) normally promotes the cell cycle.
B) normally responds to growth factors.
C) activates a signal transduction pathway.
D) inactivates growth factors.
E) does not promote cell division.

Question 36

A positive genetic test for telomerase indicates that

A) RB is inactive.
B) a cell is undergoing apoptosis.
C) proto-oncogenes have not yet mutated.
D) a cell is probably cancerous.
E) tumor suppressors are active.

Question 37

In the absence of growth factors, the retinoblastoma (RB) protein binds a transcription activator called E2F, preventing the cell from entering S stage. A mutation in E2F occurs that causes RB to no longer bind it. This mutant E2F would be considered a(n) ________.

A) oncogene
B) proto-oncogene
C) tumor suppressor
D) gain-of-function mutant
E) growth factor

Question 38

Angiogenesis contributes to carcinogenesis because

A) it allows tumor cells to spread to other parts of the body.
B) it causes blood vessels to grow into the tumor.
C) it allows tumor cells to invade underlying tissues.
D) it causes additional mutations to occur in tumor cells.
E) it causes apoptosis in tumor cells.

Question 39

Embryonic cells and cancer cells are similar because

A) DNA polymerase is inactive.
B) telomerase is active.
C) telomerase is inactive.
D) RNA polymerase is inactive.
E) proto-oncogenes are inactive.

Question 40

Many growth factors are classified as which of the following?

A) oncogenes
B) proto-oncogenes
C) tumor suppressors
D) mutant tumor suppressors
E) signal transduction pathway proteins

Question 41

Cancer cells have abnormal chromosomes because they express telomerase when they should not.

Question 42

If the maternal X chromosome is inactive and seen as Barr body in one cell, then it is the maternal X chromosome that is inactive and seen as a Barr body in every cell of that woman's body.

Question 43

In eukaryotes, one gene may specify the construction of several proteins.

Question 44

Prokaryotes regulate gene expression with a promoter.

Question 45

Cancer will occur if one copy of a mutant tumor suppressor gene is inherited.

Question 46

Stem cells that contain telomerase can be found in adults.

Question 47

Histone displacement is necessary for transcription to occur in euchromatin.

Question 48

Signal transduction pathways can stimulate transcription activators.

Question 49

Proteins are active immediately after translation occurs.

Question 50

Proto-oncogenes function by preventing cells from dividing uncontrollably.