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Ch. 24 - Cancer Genetics
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 24 - Cancer GeneticsProblem 13
Chapter 24, Problem 13

Distinguish between oncogenes and proto-oncogenes. In what ways can proto-oncogenes be converted to oncogenes?

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Define proto-oncogenes as normal genes that code for proteins involved in cell growth and division, playing a crucial role in regulating normal cellular functions.
Explain that oncogenes are mutated or abnormally expressed versions of proto-oncogenes that can lead to uncontrolled cell proliferation and contribute to cancer development.
Describe the mechanisms by which proto-oncogenes can be converted into oncogenes, including point mutations that alter the gene's function, gene amplification leading to overexpression, and chromosomal translocations that place the gene under the control of a strong promoter or create fusion proteins.
Illustrate how these changes result in the proto-oncogene gaining a 'gain-of-function' mutation, causing the protein product to be overactive or constitutively active, thereby promoting oncogenic transformation.
Summarize by emphasizing the importance of tight regulation of proto-oncogenes in normal cells and how their dysregulation through various genetic alterations leads to oncogene formation and cancer progression.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Proto-oncogenes

Proto-oncogenes are normal genes that regulate cell growth and division. They encode proteins involved in signaling pathways that promote cell proliferation and survival. Under normal conditions, they help maintain healthy cell function.
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Oncogenes

Oncogenes are mutated or abnormally expressed versions of proto-oncogenes that drive uncontrolled cell division, leading to cancer. They act dominantly to promote tumor formation by overriding normal regulatory mechanisms.
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Conversion of Proto-oncogenes to Oncogenes

Proto-oncogenes can become oncogenes through mutations, gene amplification, or chromosomal translocations. These changes can increase gene expression or produce altered proteins that continuously activate growth signals, contributing to cancer development.
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Related Practice
Textbook Question

Describe the steps by which the TP53 gene responds to DNA damage and/or cellular stress to promote cell-cycle arrest and apoptosis. Given that TP53 is a recessive gene and is not located on the X chromosome, why would people who inherit just one mutant copy of a recessive tumor-suppressor gene be at higher risk of developing cancer than those without the recessive gene?

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Textbook Question

Part of the Ras protein is associated with the plasma membrane, and part extends into the cytoplasm. How does the Ras protein transmit a signal from outside the cell into the cytoplasm? What happens in cases where the ras gene is mutated?

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Textbook Question

If a cell suffers damage to its DNA while in S phase, how can this damage be repaired before the cell enters mitosis?

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Textbook Question

Of the two classes of genes associated with cancer, tumor-suppressor genes and oncogenes, mutations in which group can be considered gain-of-function mutations? In which group are the loss-of-function mutations? Explain.

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Textbook Question

How do translocations such as the Philadelphia chromosome contribute to cancer?

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Textbook Question

Explain why many oncogenic viruses contain genes whose products interact with tumor-suppressor proteins.

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