Question 1

A headline in the June 12, 2009, issue of Science Daily proclaimed that "MicroRNA Replacement Therapy May Stop Cancer in Its Tracks." The article described a study in which a virus was used to deliver a microRNA gene to cancerous and noncancerous liver cells in mice. Aggressive liver tumors were stopped in their tracks in 8 out of 10 treated mice. Explain how delivery of a gene encoding microRNA might be able to reduce the growth of cancer cells.

Accepted Answer

MicroRNAs are small RNA molecules that p...

Question 2

A cell is unable to progress into the S phase of the cell cycle. Further studies indicate that the RB-E2F complex is unable to dissociate in this cell and thus remains together. Which of the following genes is MOST likely mutated?

Accepted Answer

A)   a gene that encodes a cyclin-dependent kinase
B)   a gene that encodes an acetylase
C)   a gene that encodes an enzyme that removes phosphate groups from RB
D)   a gene that encodes an enzyme that phosphorylates E2F
E)   a gene that encodes the Ras proteinF) A) and B)
G) A) and C)

Question 3

Certain viruses are instrumental in converting proto-oncogenes to oncogenes. This conversion most commonly results because:

Accepted Answer

A)   viruses specifically infect cells that contain proto-oncogenes.
B)   only viruses contain genes that can convert proto-oncogenes into oncogenes.
C)   the proto-oncogenes are more likely to undergo mutation or recombination within a virus.
D)   viruses contain the remainder part of the DNA that is added to the proto-oncogene to form the oncogene.E) B) and D)
F) C) and D)

Question 4

For each important checkpoint in the cell cycle, what must happen for the cycle to continue past the checkpoint?

Accepted Answer

The cell cycle is a series of phases tha...

Question 5

The increased levels of telomerase associated with many tumor cells likely promote cancer by:

Accepted Answer

A)   enhancing levels of DNA repair so that cells remain normal and have stable genomes and thus would be able to replicate their DNA and divide more often.
B)   promoting the efficiency of the spindle-assembly checkpoint.
C)   reducing the expression of several oncogenes.
D)   allowing cells to continue to divide when normally chromosomes should shorten beyond a point where division would be no longer possible.
E)   decreasing the number of epigenetic changes that would promote cancer.F) B) and E)
G) C) and D)

Question 6

A patient's cells from a colorectal polyp were collected and the APC and ras genes were analyzed. The APC gene was found to be mutated, and the ras gene was found to be up-regulated. The physician classifies the polyp an adenoma and advises the patient to have the polyp removed. The patient claims that the physician is incorrect in his advice to have the polyp removed. Is the physician's advice logical? Why or why not?

Accepted Answer

A)   no, because adenomas are benign tumors and thus are unlikely to progress to a malignant tumor
B)   no, because the up-regulation of the ras gene will counter the effects of the mutant APC gene, and the benign tumor is unlikely to progress to a malignant state
C)   no, because until the specific function of the mutated APC gene is known, it cannot be determined that the cells are in a proliferative state
D)   yes, because the cells of the polyp have already begun to divide inappropriately, and further mutations may allow the tumor to invade other tissues and metastasize
E)   yes, because up-regulation of the ras gene is causing the cells to divide more slowly, and thus they will be unable to repair future DNA damage that will likely occur in cells surrounding the polypF) B) and E)
G) A) and B)

Question 7

Consider the Ras signal-transduction pathway. Suppose that a mutation occurred within the gene that encodes the transmembrane receptor protein. Which of the following types of mutations in this receptor could lead to cancer?

Accepted Answer

A)   a mutation that allows the receptor to become phosphorylated in the absence of a growth factor bound to it
B)   a mutation in the extracellular domain that prevents the binding of a growth factor
C)   a mutation in the transmembrane domain that prevents the signal from being transduced to the interior of the cell
D)   a mutation within the intracellular domain that prevents interaction with the adaptor molecules
E)   All of these are types of receptors mutations that could lead to cancer.F) A) and C)
G) None of the above

Question 8

Most of the inherited forms of cancer involve a germline mutation in a tumor-suppressor gene while only a very few inherited cancers involve a mutation in an oncogene. What is the most reasonable explanation for this difference?

Accepted Answer

The most reasonable explanation for the ...

Question 9

Which of the following would be the result of a mutation that inactivates cyclin-E?

Accepted Answer

A)   inactivation of RB
B)   inactivation of cyclin-D
C)   inactivation of Ras
D)   failure of the cell to progress through the G2/M checkpoint
E)   failure of E2F to bind to DNA and stimulate transcriptionF) A) and D)
G) C) and D)

Question 10

If you were assigned a new form of cancer to study, you might want to determine whether it has a strong genetic basis or whether it is caused primarily by environmental factors. Propose some ways in which you could attempt to determine which hypothesis is correct. Which methods would be the easiest to use first?

Accepted Answer

There are several ways to determine whet...

Question 11

Which of the following types of cancer is associated with a defect in nucleotide-excision repair?

Accepted Answer

A)   retinoblastoma
B)   xeroderma pigmentosum
C)   cervical cancer
D)   chronic myelogenous leukemia
E)   Bloom syndromeF) A) and E)
G) B) and D)

Question 12

What are the important checkpoints in the cell cycle?

Accepted Answer

The cell cycle is a highly regulated pro...

Question 13

Which cell cycle checkpoint is most responsible for the decision of the cell to commit to dividing?

Accepted Answer

A)   the S/G2 checkpoint
B)   the G1/S checkpoint
C)   the spindle-assembly checkpoint
D)   the G2/M checkpoint
E)   the G1/G2 checkpointF) B) and E)
G) A) and D)

Question 14

Briefly describe the relationship among cyclins, cyclin-dependent kinases (CDKs), and cancer.

Accepted Answer

Cyclins are a family of proteins that re...

Question 15

What is a possible effect of mutations in genes that influence chromosome segregation during division?

Accepted Answer

A possible effect of mutations in genes ...

Question 16

Explain briefly why changes in oncogenes result in more rapid progression of a cancer compared to changes in tumor-suppressor genes. Mention one situation in which changes in a tumor-suppressor gene have a similar likelihood of causing cancer as changes in an oncogene.

Accepted Answer

Changes in oncogenes result in more rapi...

Question 17

How can defects in DNA-repair mechanisms lead to the development of cancer?

Accepted Answer

Defects in DNA-repair mechanisms can lea...

Question 18

Which of the following are regulatory molecules whose normal function is to inhibit gene expression but which often have reduced activity in many tumor cells?

Accepted Answer

A)   histones
B)   miRNAs
C)   reverse transcriptases
D)   growth factors
E)   kinasesF) A) and D)
G) C) and D)

Question 19

Which of the following statements is FALSE?

Accepted Answer

A)   Tumors usually show a clonal evolution.
B)   Cervical cancer is associated with an animal virus.
C)   Some cancers are associated with reduced DNA repair.
D)   Epigenetic changes in somatic cells may be associated with some cancers.
E)   Most tumors arise from germ-line mutations that accumulate during our life span.F) B) and D)
G) B) and E)

Question 20

Many tumor cells are able divide uncontrollably in cell culture in the laboratory. Some of these cell lines have genomes with a mutant tumor-suppressor gene. Adding a wild-type copy of this tumor-suppressor gene to the genomes of these cells reduces their ability to divide in culture. In contrast, adding a wild-type copy of a proto-oncogene to the genomes of a tumor cell line with an activated oncogene doesn't have any effect on the uncontrolled cell division shown by this line. Which of the following statements BEST explains why adding a wild-type proto-oncogene doesn't affect cell division in these cell lines?

Accepted Answer

A)   Most point mutations that produce activated oncogenes are dominant gain-of-function mutations.
B)   Many proto-oncogenes encode proteins that act to promote apoptosis.
C)   Many proto-oncogenes encode proteins involved in DNA repair.
D)   Many proto-oncogenes are inherited as recessive mutations.
E)   Most protein products of proto-oncogenes don't have a role in cell division.F) A) and B)
G) C) and E)

Exam 23: Cancer Genetics

Which cell cycle checkpoint is most responsible for the decision of the cell to commit to dividing?

Correct Answer
verified

For each important checkpoint in the cell cycle, what must happen for the cycle to continue past the checkpoint?

Correct Answer
Answered by ExamLex AI
The cell cycle is a series of phases tha...
View Answer

Explain briefly why changes in oncogenes result in more rapid progression of a cancer compared to changes in tumor-suppressor genes. Mention one situation in which changes in a tumor-suppressor gene have a similar likelihood of causing cancer as changes in an oncogene.

Correct Answer
Answered by ExamLex AI
Changes in oncogenes result in more rapi...
View Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
MicroRNAs are small RNA molecules that p...
View Answer

Which of the following statements is FALSE?

Correct Answer
verified

Consider the Ras signal-transduction pathway. Suppose that a mutation occurred within the gene that encodes the transmembrane receptor protein. Which of the following types of mutations in this receptor could lead to cancer?

Correct Answer
verified

What are the important checkpoints in the cell cycle?

Correct Answer
Answered by ExamLex AI
The cell cycle is a highly regulated pro...
View Answer

Which of the following would be the result of a mutation that inactivates cyclin-E?

Correct Answer
verified

How can defects in DNA-repair mechanisms lead to the development of cancer?

Correct Answer
Answered by ExamLex AI
Defects in DNA-repair mechanisms can lea...
View Answer

Correct Answer
Answered by ExamLex AI
There are several ways to determine whet...
View Answer

Which of the following are regulatory molecules whose normal function is to inhibit gene expression but which often have reduced activity in many tumor cells?

Correct Answer
verified

The increased levels of telomerase associated with many tumor cells likely promote cancer by:

Correct Answer
verified

Certain viruses are instrumental in converting proto-oncogenes to oncogenes. This conversion most commonly results because:

Correct Answer
verified

Most of the inherited forms of cancer involve a germline mutation in a tumor-suppressor gene while only a very few inherited cancers involve a mutation in an oncogene. What is the most reasonable explanation for this difference?

Correct Answer
Answered by ExamLex AI
The most reasonable explanation for the ...
View Answer

Briefly describe the relationship among cyclins, cyclin-dependent kinases (CDKs), and cancer.

Correct Answer
Answered by ExamLex AI
Cyclins are a family of proteins that re...
View Answer

A cell is unable to progress into the S phase of the cell cycle. Further studies indicate that the RB-E2F complex is unable to dissociate in this cell and thus remains together. Which of the following genes is MOST likely mutated?

Correct Answer
verified

Correct Answer
verified

What is a possible effect of mutations in genes that influence chromosome segregation during division?

Correct Answer
Answered by ExamLex AI
A possible effect of mutations in genes ...
View Answer

Which of the following types of cancer is associated with a defect in nucleotide-excision repair?

Correct Answer
verified

Exam 23: Cancer Genetics

Which cell cycle checkpoint is most responsible for the decision of the cell to commit to dividing?

Correct AnswerverifiedShow Answer

For each important checkpoint in the cell cycle, what must happen for the cycle to continue past the checkpoint?

Correct AnswerAnswered by ExamLex AIThe cell cycle is a series of phases tha...View AnswerShow Answer

Explain briefly why changes in oncogenes result in more rapid progression of a cancer compared to changes in tumor-suppressor genes. Mention one situation in which changes in a tumor-suppressor gene have a similar likelihood of causing cancer as changes in an oncogene.

Correct AnswerAnswered by ExamLex AIChanges in oncogenes result in more rapi...View AnswerShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerAnswered by ExamLex AIMicroRNAs are small RNA molecules that p...View AnswerShow Answer

Which of the following statements is FALSE?

Correct AnswerverifiedShow Answer

Consider the Ras signal-transduction pathway. Suppose that a mutation occurred within the gene that encodes the transmembrane receptor protein. Which of the following types of mutations in this receptor could lead to cancer?

Correct AnswerverifiedShow Answer

What are the important checkpoints in the cell cycle?

Correct AnswerAnswered by ExamLex AIThe cell cycle is a highly regulated pro...View AnswerShow Answer

Which of the following would be the result of a mutation that inactivates cyclin-E?

Correct AnswerverifiedShow Answer

How can defects in DNA-repair mechanisms lead to the development of cancer?

Correct AnswerAnswered by ExamLex AIDefects in DNA-repair mechanisms can lea...View AnswerShow Answer

Correct AnswerAnswered by ExamLex AIThere are several ways to determine whet...View AnswerShow Answer

Which of the following are regulatory molecules whose normal function is to inhibit gene expression but which often have reduced activity in many tumor cells?

Correct AnswerverifiedShow Answer

The increased levels of telomerase associated with many tumor cells likely promote cancer by:

Correct AnswerverifiedShow Answer

Certain viruses are instrumental in converting proto-oncogenes to oncogenes. This conversion most commonly results because:

Correct AnswerverifiedShow Answer

Most of the inherited forms of cancer involve a germline mutation in a tumor-suppressor gene while only a very few inherited cancers involve a mutation in an oncogene. What is the most reasonable explanation for this difference?

Correct AnswerAnswered by ExamLex AIThe most reasonable explanation for the ...View AnswerShow Answer

Briefly describe the relationship among cyclins, cyclin-dependent kinases (CDKs), and cancer.

Correct AnswerAnswered by ExamLex AICyclins are a family of proteins that re...View AnswerShow Answer

A cell is unable to progress into the S phase of the cell cycle. Further studies indicate that the RB-E2F complex is unable to dissociate in this cell and thus remains together. Which of the following genes is MOST likely mutated?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

What is a possible effect of mutations in genes that influence chromosome segregation during division?

Correct AnswerAnswered by ExamLex AIA possible effect of mutations in genes ...View AnswerShow Answer

Which of the following types of cancer is associated with a defect in nucleotide-excision repair?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The cell cycle is a series of phases tha...
View Answer

Correct Answer
Answered by ExamLex AI
Changes in oncogenes result in more rapi...
View Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
MicroRNAs are small RNA molecules that p...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The cell cycle is a highly regulated pro...
View Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
Defects in DNA-repair mechanisms can lea...
View Answer

Correct Answer
Answered by ExamLex AI
There are several ways to determine whet...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The most reasonable explanation for the ...
View Answer

Correct Answer
Answered by ExamLex AI
Cyclins are a family of proteins that re...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
A possible effect of mutations in genes ...
View Answer

Correct Answer
verified