APPLICATION QUESTIONS AND PROBLEMS

Introduction

Question 15

15.What characteristics of the pedigree shown in Figure 16.1 suggest that pancreatic cancer in this family is inherited as an autosomal dominant trait?

Section 16.1

Question 16

16.If cancer is fundamentally a genetic disease, how might an environmental factor such as smoking cause cancer?

Question 17

*17.Both genes and environmental factors contribute to cancer. Prostate cancer is 30 times more common among people in Utah than among people in Shanghai (see Table 16.2). Briefly outline how you might determine whether these differences in the incidence of prostate cancer are due to differences in the genetic makeup of the two populations or to differences in their environments.

Question 18

*18.A couple has one child with bilateral retinoblastoma. The mother is free from cancer, but the father has unilateral retinoblastoma, and he has a brother who has bilateral retinoblastoma.

  1. If the couple has another child, what is the probability that this next child will have retinoblastoma?

  2. If the next child has retinoblastoma, is it likely to be bilateral or unilateral?

  3. Explain why the father’s case of retinoblastoma is unilateral, whereas his son’s and brother’s cases are bilateral.

Section 16.2

Question 19

*19.The palladin gene, which plays a role in pancreatic cancer (see the introduction to this chapter), is said to be an oncogene. Which of its characteristics suggest that it is an oncogene rather than a tumor-suppressor gene?

Question 20

20.Mutations in the RB gene are often associated with cancer. Explain how a mutation that results in a nonfunctional RB protein contributes to cancer.

Question 21

21.Cells in a tumor contain mutated copies of a particular gene that promotes tumor growth. Gene therapy can be used to introduce a normal copy of this gene into the tumor cells. Would you expect this therapy to be effective if the mutated gene were an oncogene? A tumor-suppressor gene? Explain your reasoning.

Question 22

22.Some cancers have been treated with drugs that demethylate DNA. Explain how these drugs might work. Do you think the cancer-causing genes that respond to the demethylation are likely to be oncogenes or tumor-suppressor genes? Explain your reasoning.

Section 16.4

Question 23

23.Some cancers are consistently associated with the deletion of a particular part of a chromosome. Does the deleted region contain an oncogene or a tumor-suppressor gene? Explain.