Chapter 20 Cell BIo

A malignant tumor is more dangerous than a benign tumor because

• its cells proliferate faster.

• it causes neighboring cells to mutate.

• its cells attack and phagocytose neighboring normal tissue cells.

• its cells invade other tissues.

What part of an epithelial tissue needs to be degraded to allow tumor cells to spread to the rest of the body?

• tight junctions

• apical membrane proteins

• integrin receptors

• basal lamina

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

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

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

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

• 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.

Which of the following statements about cancer is FALSE?

• Viruses cause some cancers.

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

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

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

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)

• tumor suppressor.

• oncogene.

• proto-oncogene.

• gain-of-function mutation.

Mouse embryonic stem (ES) cells

• can only be grown in the laboratory.

• can give rise to all tissues and cell types in the body except germ cells.

• can be made in the lab from human iPS cells.

• come from the inner cell mass of early embryos.

An adult hemopoietic stem cell found in the bone marrow

• will occasionally produce epidermal cells when necessary.

• can produce only red blood cells.

• can undergo self-renewing divisions for the lifetime of a healthy animal.

• will express all the same transcription factors as those found in an unfertilized egg.

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

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

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

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

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

You have a recessive mutation in the cell that causes excess cell survival. Which scenario has made this possible?

• An activating mutation in a growth factor receptor

• Overexpression of a proto-oncogene due to gene amplification

• An activating mutation that converts a proto-oncogene into an oncogene

• Loss-of-function in a tumor suppressor gene due to inactivation of both alleles

Which combination would cause an excessive proliferation of gut stem cells?

• Low Wnt proteins and rapid degradation of β-catenin

• Excess APC activity leading to constant β-catenin destruction

• Excess Wnt proteins and B-catenin in the cell

• High levels of differentiation signals such as BMP and Notch inhibition