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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Ch. 19 - The Genetics of Cancer
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 19, Problem 21
Radiotherapy (treatment with ionizing radiation) is one of the most effective current cancer treatments. It works by damaging DNA and other cellular components. In which ways could radiotherapy control or cure cancer, and why does radiotherapy often have significant side effects?
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Understand that radiotherapy controls or cures cancer primarily by causing damage to the DNA of cancer cells, leading to cell death or preventing their ability to divide and proliferate.
Recognize that ionizing radiation induces DNA double-strand breaks and other types of damage, which, if unrepaired or misrepaired, trigger apoptosis (programmed cell death) or senescence in cancer cells.
Consider that radiotherapy targets rapidly dividing cells, which is a characteristic of many cancer cells, making them more susceptible to DNA damage compared to most normal cells.
Acknowledge that significant side effects occur because radiotherapy can also damage normal, healthy cells in the surrounding tissues, especially those that also divide rapidly, such as cells in the skin, gastrointestinal tract, and bone marrow.
Note that the extent of side effects depends on factors like radiation dose, treatment area, and individual patient sensitivity, which explains why side effects can vary widely among patients.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mechanism of DNA Damage by Ionizing Radiation
Ionizing radiation used in radiotherapy causes breaks in DNA strands, especially double-strand breaks, which can lead to cell death or malfunction. Cancer cells, which divide rapidly, are more susceptible to this damage, leading to their destruction or growth inhibition.
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04:29
Induced Mutations
Selective Targeting of Cancer Cells
Radiotherapy aims to target cancer cells more than normal cells by exploiting differences like rapid division and impaired DNA repair in tumors. However, some normal cells near the tumor are also affected, which limits the dose and effectiveness.
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09:46Cancer Characteristics
Side Effects Due to Damage of Normal Cells
Radiotherapy can harm healthy tissues surrounding the tumor, causing side effects such as inflammation, fatigue, and tissue damage. These effects arise because normal cells also experience DNA and cellular damage, especially in rapidly dividing tissues like skin and mucosa.
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Related Practice
Textbook Question
How do translocations such as the Philadelphia chromosome contribute to cancer?
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Textbook Question
How do normal cells protect themselves from accumulating mutations in genes that could lead to cancer? How do cancer cells differ from normal cells in these processes?
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Textbook Question
Genetic tests that detect mutations in the BRCA1 and BRCA2 tumor-suppressor genes are widely available. These tests reveal a number of mutations in these genes—mutations that have been linked to familial breast cancer. Assume that a young woman in a suspected breast cancer family takes the BRCA1 and BRCA2 genetic tests and receives negative results. That is, she does not test positive for the mutant alleles of BRCA1 or BRCA2. Can she consider herself free of risk for breast cancer?
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Textbook Question
As part of a cancer research project, you have discovered a gene that is mutated in many metastatic tumors. After determining the DNA sequence of this gene, you compare the sequence with those of other genes in the human genome sequence database. Your gene appears to code for an amino acid sequence that resembles sequences found in some serine proteases. Conjecture how your new gene might contribute to the development of highly invasive cancers.
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