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Chapter 8: Problem 8

Of the following scenarios, which is most likely to increase the odds that a cancer will develop? a. One copy of a proto-oncogene is mutated such that it becomes nonfunctional. b. One copy of a tumor suppressor gene is mutated such that it becomes nonfunctional. c. One copy of an oncogene is hyperactive. d. Two copies of a tumor suppressor gene are hyperactive.

Short Answer

Expert verified
Option c is most likely to increase cancer risk.

Step by step solution

01

Understanding Key Concepts

First, we need to understand what proto-oncogenes, tumor suppressor genes, and oncogenes are. Proto-oncogenes are normal genes that, when mutated, can become oncogenes and cause the cell to grow uncontrollably. Tumor suppressor genes typically prevent cell growth, and both copies must usually be nonfunctional for a cancer to develop. Oncogenes promote cell division and survival, and even a single hyperactive copy can increase cancer risk.
02

Evaluate Option a

Option a states that one copy of a proto-oncogene is mutated such that it becomes nonfunctional. Proto-oncogenes need to be activated (or gain function) to promote cancer, so making one nonfunctional (loss of function) is less likely to cause cancer.
03

Evaluate Option b

Option b states that one copy of a tumor suppressor gene is mutated such that it becomes nonfunctional. Typically, both copies of a tumor suppressor gene must be mutated (knocked out) to significantly increase cancer risk. Therefore, one nonfunctional copy is unlikely to do this alone.
04

Evaluate Option c

Option c describes one copy of an oncogene being hyperactive. Since oncogenes promote cell growth, even a single hyperactive oncogene can significantly increase the odds of cancer developing.
05

Evaluate Option d

Option d mentions two copies of a tumor suppressor gene being hyperactive. Hyperactive tumor suppressor genes would even more so prevent rapid cell division and cancer, so this scenario is least likely to contribute to cancer development.
06

Determine Most Likely Scenario

After evaluating all options, option c (one copy of an oncogene is hyperactive) is most likely to increase cancer risk. Oncogenes need only one hyperactive copy to lead to excessive cell growth and contribute to cancer.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Proto-Oncogenes
Proto-oncogenes are like the genes that give a green light for cell growth and division. They play a crucial role in normal cell functions, helping with cell repair and renewal. However, things can get tricky when mutations alter these genes.
  • Under normal conditions, proto-oncogenes help maintain regulated cell growth.
  • If a proto-oncogene mutates into an oncogene, it can push cells to grow uncontrollably, potentially leading to cancer.
  • Interestingly, if one copy of a proto-oncogene becomes nonfunctional, it usually doesn't immediately lead to cancer because its action needs to be active or overactive to pose a risk.
Understanding proto-oncogenes is important since they are often the precursors to oncogenes, setting the stage for possible cellular imbalance and disease.
Tumor Suppressor Genes
Tumor suppressor genes act as the brakes of cell growth and division. They are essential for stopping cells from growing out of control and becoming cancerous. If these genes fail, it is like losing control over cell division.
  • These genes help repair DNA, induce cell death when necessary, and ensure cells do not divide too quickly.
  • Typically, both copies of a tumor suppressor gene need to be mutated for a substantial increase in cancer risk.
  • One nonfunctional copy alone is generally insufficient to lead to cancer, since the remaining functional copy can often compensate.
Thus, the safeguard function of tumor suppressor genes is vital as they significantly reduce the risk of uncontrolled cell proliferation, keeping cancer at bay.
Oncogenes
Oncogenes are the bad guys in cancer biology. When proto-oncogenes mutate to become oncogenes, they drive cells to multiply excessively.
  • Even a single hyperactive oncogene can lead to unregulated cell division, making it a potent factor in cancer development.
  • Such a mutation can result in the production of proteins that force cells to continue dividing without the usual checks and balances.
  • As a result, the presence of only one altered oncogene can significantly tip the scales toward cancerous growth.
Therefore, understanding the role of oncogenes highlights why their regulation is crucial in maintaining cellular health and preventing cancer.
Cancer Risk Factors
Cancer risk factors encompass a variety of elements that can increase the likelihood of developing cancer. Some risk factors are genetic, while others are environmental or lifestyle-related.
  • Genetic predispositions can include mutations in oncogenes or tumor suppressor genes.
  • Lifestyle choices such as smoking, diet, and physical activity can also play a significant role.
  • Environmental exposures like radiation and pollutants can increase risk.
  • Additionally, certain infections, such as the human papillomavirus (HPV), are known risk factors for cancer development.
Understanding and managing these risk factors can effectively reduce the likelihood of cancer, emphasizing the importance of preventive measures and regular screenings.

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Most popular questions from this chapter

Growth factors a. can only stimulate cell division, not restrain it. b. are signaling molecules that affect cell division. c. function as positive growth regulators, but not as negative growth regulators. d. function as negative growth regulators, but not as positive growth regulators.

Why is cancer more common in older people than in younger people? a. It takes many cells to produce a cancer, and older people have more cells. b. The DNA of older people is more susceptible to carcinogens. c. Our immune system becomes stronger as we age. d. Multiple genes must pick up harmful mutations for cancer to develop, and that takes time.

Which of the following is the last step in the development of a cancer? a. anchorage independence c. metastasis b. loss of cell adhesion d. cell proliferation

The majority of human cancers a. are hereditary (caused by the inheritance of mutated genes). b. are the result of infection with oncogenic viruses. c. arise from multiple somatic mutations accumulating in a single cell. d. are caused by the normal activity of proto-oncogenes.

Which of the following is an example of a negative growth regulator? a. human growth hormone, which stimulates cell division in bone b. human growth hormone receptor, which is part of the signal transduction pathway for the hormone c. prostate-specific antigen, which is a tumor marker found on the surface of prostate cancer cells d. transforming growth factor beta (TGF-\beta), which blocks the cell cycle when there is DNA damage
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