Question 1

Describe Knudson's two-mutation model: When and where are the mutations posited to occur?

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Question 2

Programmed cell death,or apoptosis,is a necessary and useful property of cells.Why is this so?

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Question 3

List the ways in which proto-oncogenes may be converted to oncogenes.

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Question 4

Most cancer deaths in the United States are caused by radiation-induced cancer.

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While radiation exposure can increase the risk of developing certain types of cancer, the majority of cancer deaths in the United States are not caused by radiation-induced cancer. The most common causes of cancer deaths in the US are lung cancer, colorectal cancer, and breast cancer.

Question 5

How does telomerase,which is not a cause of cancer,nonetheless play a role in its development?

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Question 6

Inherited mutant tumor suppressors produce a dominant susceptibility to cancer,but the mutant alleles are actually recessive in the cancer.

Accepted Answer

Inherited mutant tumor suppressors, such as BRCA1 and BRCA2, produce a dominant susceptibility to cancer, which means that individuals with just one mutation in the tumor suppressor gene have an increased risk of developing cancer. However, in order for the cancer to actually develop, both copies of the gene (one from each parent) must be mutated, making the mutant alleles recessive in the cancer itself.

Question 7

Terminally differentiated cells are noncancerous,normal cells.

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Terminally differentiated cells are fully specialized cells, meaning they have reached their final stage of development and are noncancerous.

Question 8

The nucleic acid of retroviral provirus is composed of RNA.

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The nucleic acid of a retroviral provirus is composed of DNA, which is integrated into the host cell's DNA. Retroviruses convert their RNA genome into DNA using reverse transcriptase.

Question 9

The process of relaying a growth-stimulatory or growth-inhibitory signal in response to an extracellular factor binding at the cell surface is called intercellular signaling.

Accepted Answer

The process described is known as intracellular signaling, which involves the transmission of signals inside a cell in response to the binding of extracellular factors to cell surface receptors. Intercellular signaling refers to the communication between cells.

Question 10

People with the genetic disease xeroderma pigmentosum have compromised DNA repair mechanisms,making them extremely sensitive to genetic damage from sunlight.Without taking measures to minimize exposure,these individuals typically succumb to skin cancer in childhood or early adulthood-a demonstration of the mutagenicity of ultraviolet radiation.Yet,deliberate exposure in the form of sunbathing is very popular with some segments of the population.Why do you think this is so,and how might public health professionals raise awareness of the danger in which these people place themselves?

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Question 11

Some carcinogens act on the genome directly,while others are converted to mutagenic substances by the cells's enzymes.

Accepted Answer

This statement is true. Some carcinogens, such as radiation and certain chemicals, can act directly on the DNA within cells, causing mutations and potentially leading to cancer. Other carcinogens, such as some tobacco smoke components, are metabolized by the body's enzymes into mutagenic substances that can cause DNA damage and increase cancer risk.

Question 12

Ionizing radiation is emitted at low levels by many natural objects,including some rocks and gases.

Accepted Answer

This statement is true. Natural sources of ionizing radiation include rocks containing uranium or thorium, radon gas, and cosmic radiation from space.

Question 13

The Bcl-2 gene product in its normal form can be activated to prevent cells from undergoing apoptosis (programmed cell death)in specific circumstances.It is a carefully regulated gene,being "turned on" only under specific circumstances.A null mutation in Bcl-2 leads to excessive cell loss.Some Bcl-2 mutation can cause a "gain of function" in which the protein is active all the time.
a.In the terms used in this chapter,what would the normal version be called?
b.What would the gain-of-function mutation be called?
c.How would you expect the gain-of-function mutation to be involved in cancer?

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Question 14

Wild-type mutator genes produce substances that induce point mutations and chromosomal rearrangements.

Accepted Answer

Wild-type mutator genes actually work to maintain the integrity of the genetic material by correcting errors that occur during DNA replication, not inducing mutations or chromosomal rearrangements.

Question 15

The only genes necessary for the retroviral lifecycle are gag and pol.

Accepted Answer

Along with gag and pol, retroviruses also require the gene env for its lifecycle, which codes for the viral envelope protein responsible for binding to host cells.

Question 16

In normal cells,p53 protein acts as

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...

Question 17

The products of tumor suppressor genes stimulate cell proliferation,while the products of proto-oncogenes inhibit cell proliferation.

Accepted Answer

The statement is actually the opposite of what is true - tumor suppressor genes inhibit cell proliferation, while proto-oncogenes stimulate cell proliferation.

Question 18

When oncologists (scientists who study cancer)refer to "transformation," they mean something different from what the word "transformation" signifies when used by biotechnologists.Explain the difference between the two uses of the term in genetics.

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Question 19

The terms proto-oncogene and oncogene may give the misleading impression that these are "genes for cancer" that are waiting to be turned on.What are these genes,in terms of normal function,and what name might have been given to them to reflect this function rather than their role in cancer?

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Question 20

What is metastasis,and why is metastatic cancer the most difficult cancer to treat?

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Quiz 20: Genetics of Cancer