Comprehension Questions

Section 23.1

Question 23.1

What types of evidence indicate that cancer arises from genetic changes?

Question 23.2

How is cancer different from most other types of genetic diseases?

Question 23.3

Outline Knudson’s two-hit hypothesis of retinoblastoma and describe how it helps to explain unilateral and bilateral cases of retinoblastoma.

Question 23.4

Briefly explain how cancer arises through clonal evolution.

Section 23.2

Question 23.5

What is the difference between an oncogene and a tumor-suppressor gene? Give some examples of the functions of proto-oncogenes and tumor suppressers in normal cells.

Question 23.6

What is haploinsufficiency? How might it affect cancer risk?

Question 23.7

How do cyclins and CDKs differ? How do they interact in controlling the cell cycle?

Question 23.8

Briefly outline the events that control the progression of cells through the G1/S checkpoint in the cell cycle.

Question 23.9

Briefly outline the events that control the progression of cells through the G2/M checkpoint of the cell cycle.

Question 23.10

What is a signal-transduction pathway? Why are mutations in components of signal-transduction pathways often associated with cancer?

Question 23.11

How is the Ras protein activated and inactivated?

Question 23.12

Why do mutations in genes that encode DNA-repair enzymes often produce a predisposition to cancer?

Question 23.13

What role do telomeres and telomerase play in cancer progression?

Section 23.3

Question 23.14

How is an epigenetic change different from a mutation?

Question 23.15

How is DNA methylation related to cancer?

Section 23.4

Question 23.16

Briefly outline some of the genetic changes commonly associated with the progression of colorectal cancer.

Section 23.5

Question 23.17

Explain how chromosome deletions, inversions, and translocations may cause cancer.

Question 23.18

Briefly outline how the Philadelphia chromosome leads to chronic myelogenous leukemia.

Question 23.19

What is genomic instability? Give some ways in which genomic instability may arise.

Section 23.6

Question 23.20

How do viruses contribute to cancer?

For more questions that test your comprehension of the key chapter concepts, go to for this chapter.