Molecular Cell Bio Chapter 20

Which of the following types of cell-surface receptor activates the Ras and MAP kinase pathway necessary for cell-cycle progression and tumor growth?

 

1. G-protein coupled receptor

2. adherin junctions

3. receptor tyrosine kinase receptors

4. integrin receptors

3

A malignant tumor is more dangerous than a benign tumor because

 

1. its cells proliferate faster.

2. it causes neighboring cells to mutate.

3. its cells attack and phagocytose neighboring normal tissue cells.

4. its cells invade other tissues.

4

Which of the following statements about cancer is FALSE?

 

1. Viruses cause some cancers.

2. Tobacco use is responsible for more than 20% of all cancer deaths.

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

4. Chemical carcinogens cause cancer by changing the nucleotide sequence of DNA.

3

Which of the following genetic changes CANNOT convert a proto-oncogene into an oncogene?

 

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

2. A mutation within the coding sequence that makes the protein hyperactive.

3. An amplification of the number of copies of the proto-oncogene, causing overproduction of the normal protein.

4. A mutation in the promoter of the proto-oncogene, causing the normal protein to be transcribed and translated at an abnormally high level.

1

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?

 

1. Like the mice lacking TCF4, they will not be able to renew the gut lining.

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

3. Mice lacking the Apc gene will have a hyperactive Wnt receptor even though there is no Wnt signal.

4. 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.

2

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(n)

 

1. tumor suppressor.

2. oncogene.

3. proto-oncogene.

4. gain-of-function mutation.

3

A metastasis is

 

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

2. a cell that is dividing in defiance of normal constraints.

3. a part of the primary tumor that has invaded the surrounding tissue.

4. the portion of the cancerous tumor that displays genetic instability.

1

Which of the following statements about tumor suppressor genes is FALSE?

 

1. Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-oncogene.

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

3. Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation.

4. 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.

2

What must take place for tumor cells in an epithelial cell layer to spread and become invasive to other organs of the body?

 

1. The cells must inactivate telomerase so that chromosomal integrity can be maintained.

2. Some of the cells undergo additional DNA damage, leading to less glycosaminoglycan synthesis and a thinner, more easily penetrable basal lamina.

3. A few of the tumor cells gain a mutation by chance, which activates a proteolytic enzyme (a protease) that degrades the basal lamina.

4. The endothelial cells of blood vessels must mutate and penetrate through the basal lamina of an epithelial cell layer, which allows the tumor cells access to the circulatory system.

3

Cells that are terminally differentiated

 

1. will undergo apoptosis within a few days.

2. can no longer undergo cell division.

3. are unable to move.

4. no longer produce RNAs.

2