Question 1

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

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Question 2

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

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Question 3

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

The physician's advice is logical because mutations in the APC gene and up-regulation of the ras gene are associated with inappropriate cell division, increasing the risk of the polyp progressing to a malignant state. Removing the polyp can prevent further mutations and potential metastasis.

Question 4

Explain how DNA sequencing studies can aid in our understanding of cancer formation.

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Question 5

Which of the following chromosomal abnormalities is associated with chronic myelogenous leukemia?

Accepted Answer

Chronic myelogenous leukemia (CML) is associated with a reciprocal translocation between chromosome 9 and chromosome 22, known as the Philadelphia chromosome.

Question 6

In Burkitt lymphoma, there is increased expression of the MYC gene. Which of the following statements BEST explains the reason for the increased expression of this gene?

Accepted Answer

In Burkitt lymphoma, a translocation typically occurs between chromosome 8 and 14, bringing the MYC gene under the control of the immunoglobulin heavy chain enhancer, leading to its increased expression.

Question 7

Chromosome mutations are common in tumor cells. Do these mutations cause cancer, or are they a result of cancer? What evidence is there for your conclusion?

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Question 8

Distinguish between driver and passenger mutations in cancer genomes. Propose a strategy whereby "knock-in" technology (Chapter 19) could be used to distinguish between driver and passenger mutations. What might be a major limitation to this strategy?

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Question 9

A cancer cell line was identified as having inappropriate expression of telomerase. Which of the following would be the BEST treatment that could make this cell line mortal?

Accepted Answer

Methylating the promoter of the telomerase gene would likely reduce its expression, potentially making the cancer cell line mortal by limiting its ability to maintain telomere length.

Question 10

What is angiogenesis? Why are mutations involving angiogenesis associated with tumors?

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Question 11

What are the important checkpoints in the cell cycle?

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Question 12

What are two processes that determine how quickly mutations accumulate within a cell?

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Question 13

In cancer, mutations in stimulatory genes (such as in proto-oncogenes) are often dominant, whereas mutations in inhibitory genes (such as tumor-suppressor alleles) are often recessive. Why?

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Question 14

What is unique to the DNA changes observed in the Apaf-1 gene in malignant melanoma cells? What are such changes to DNA called, and why do you think these types of changes in cancer have caught researchers' attention?

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Question 15

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.

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Question 16

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

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Question 17

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.

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Question 18

Which of the following statements BEST characterizes many cancers such as colon cancer?

Accepted Answer

Many cancers, including colon cancer, result from a series of sequential mutations in multiple genes, leading to uncontrolled cell growth and division.

Question 19

Explain how hypermethylation and hypomethylation may be associated with cancers.

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Question 20

Retinoblastoma (RB) protein is important in regulating the cell cycle. It must be completely phosphorylated before the cell can move from the G₁ phase to the S phase of the cell cycle. Retinoblastoma is a type of cancer. Based on this information, what do you think goes wrong in retinoblastoma?

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Quiz 23: Cancer Genetics