Quiz 15

For each mutant, choose whether the mutation will lead to cell cycle arrest, cell cycle progression or have no effect on the cell cycle. 1. A G1-Cdk is active regardless of its phosphorylation state. 2. A mitogen receptor is constitutively active, even in the absence of its cognate mitogen. 3. A mutation in Rb that prevents it from being phosphorylated. 4. A mutation in the active site of an S-Cdk. 5. A mutation in Rb that disrupts its binding to its substrate.

1. Cell cycle progression 2. Cell cycle progression 3. Cell cycle arrest 4. Cell cycle arrest 5. Cell cycle progression

Which of the following statements about tumor suppressor genes is false? Select one: a. Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells. b. Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two functional copies of a tumor suppressor gene. c. Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-oncogene. d. Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation.

a. Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.

Suppose you are working in a lab that wishes to develop a drug to treat people with colorectal cancer. Assuming that most human colorectal tumors harbor mutations in the APC gene, which protein from the pathway would be a good target for an activity-blocking anticancer drug? Select one or more: a. beta-catenin b. the Wnt receptor c. the signaling molecule activated by the Wnt receptor d. TCF

a. beta-catenin d. TCF

Jurkat T cells were either left untreated or treated with staurosporine for 18 hr and then stained with Annexin-FITC and PI. The FACS results are shown in the Figure. Choose the appropriate conclusion. a. About 40% of the cells became noticeably larger in response to staurosporine. b. About 40% of the cells became apoptotic in response to staurosporine. c. About 40% of the cells became necrotic in response to staurosporine. d. About 40% of the cells became both apoptotic and necrotic in response to staurosporine.

b. About 40% of the cells became apoptotic in response to staurosporine.

Which of the following statements about apoptosis is true? Select one: a. The prodomain of procaspases contains the catalytic activity necessary for procaspase activation. b. Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria. c. Cells that constitutively express Bcl2 will be more prone to undergo apoptosis. d. Bax and Bak promote apoptosis by binding to procaspases in the apoptosome.

b. Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.

Which comparison best supports the idea that cancer may be due to environmental factors? Select one: a. Comparing prostate cancer rates in Hawaiian Japanese and Hawaiian Caucasians. b. Comparing stomach cancer rates in Osaka Japan and in Japanese Hawaiians. c. Comparing prostate cancer rates to stomach cancer rates in Hawaiian Caucasians. d. Comparing stomach cancer rates in people from Osaka during 1970-71 vs 1988-1992.

b. Comparing stomach cancer rates in Osaka Japan and in Japanese Hawaiians.

Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the normal Ras gene is a/an _____. Select one: a. oncogene b. proto-oncogene c. mitogen d. tumor suppressor gene

b. proto-oncogene

Programmed cell death occurs _____.

by means of an intracellular suicide program

A metastasis is _____.

a secondary tumor in a different part of the body that arises from a cell from the primary tumor

Which of the following statements about cancer is false?

a. A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.

Which of the following proteins inhibits apoptosis? Select one: a. Bcl2 b. Bad c. Bax d. cytochrome c

a. Bcl2

Which of the following genetic changes cannot convert a proto-oncogene into an oncogene? Select one: a. An amplification of the number of copies of the proto-oncogene, causing overproduction of the normal protein b. A mutation within the coding sequence that makes the protein hyperactive c. A mutation that introduces a stop codon immediately after the codon for the initiator methionine d. A mutation in the promoter of the proto-oncogene, causing the normal protein to be transcribed and translated at an abnormally high level

c. A mutation that introduces a stop codon immediately after the codon for the initiator methionine

A certain mutation in the receptor for epidermal growth factor (EGF) causes the mutated receptor protein to send a positive signal along the associated intracellular signaling pathway even when the EGF ligand is not bound to it. This signal leads to abnormal cell proliferation in the absence of growth factor. Which of the following statements is true? Select one: a. The gene for the mutant EGF receptor is a proto-oncogene. b. The gene for EGF receptor is a tumor suppressor gene. c. The gene for this mutant EGF receptor is an oncogene. d. Deletion of the gene for EGF receptor would also lead to uncontrolled cell proliferation.

c. The gene for this mutant EGF receptor is an oncogene.

APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the TCF complex from turning on Wnt-responsive genes. Mice that lack the gene encoding TCF4 do not have the ability to maintain the pool of proliferating gut stem cells needed to renew the gut lining. What do you predict will happen in mice that lack the APC gene? Select one: a. Like the mice lacking TCF4, they will not be able to renew the gut lining. b. Mice lacking the APC gene will have a hyperactive Wnt receptor even though there is no Wnt signal. c. They will have inappropriate proliferation of gut stem cells. d. Mice lacking the APC gene will be like normal healthy mice, since APC is a tumor suppressor and thus not needed unless there is a tumor present.

c. They will have inappropriate proliferation of gut stem cells.

Irradiated mammalian cells usually stop dividing and arrest at a G1 checkpoint. Place the following events in the order in which they occur.

first → DNA damage, second → accumulation and activation of p53, third → production of p21, fourth → inhibition of cyclin-Cdk complexes

The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by ______.

inhibiting cyclin transcription

Survival factor

inhibits apoptosis by regulating members of the Bcl2 family

Myostatin

inhibits muscle growth

A malignant tumor is more dangerous than a benign tumor because ______________________.

its cells invade other tissues

Mitogen

stimulates cell division by releasing the molecular brakes that keep cells in G1

When cells enter G0, they _____.

stop dividing

Apoptosis differs from necrosis in that necrosis ________________.

Causes cells to swell and burst, whereas apoptotic cells shrink and condense

Growth factor

Stimulates biosynthesis and an increase in cell mass