Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

19. Cancer Genetics

Cancer Mutations

Genetics

19. Cancer Genetics

Cancer Mutations

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2:16 minutes

Problem 30

Textbook Question

Although cancer is not a contagious disease in humans or other vertebrates, there have been rare cases in which cancers have spread from one organism to another. Describe three cases of these contagious cancers and what conditions might have led to their appearance.

Verified step by step guidance

Understand the concept of contagious cancers: While cancer is generally not contagious, there are rare cases where cancer cells can spread between individuals under specific conditions. These cases are typically observed in certain animal species and involve direct transmission of cancer cells.

Case 1: Tasmanian Devil Facial Tumor Disease (DFTD): This is a transmissible cancer affecting Tasmanian devils. It spreads through biting during social interactions, where cancer cells are physically transferred from one individual to another. The lack of genetic diversity in Tasmanian devils may contribute to the immune system's inability to recognize and reject the foreign cancer cells.

Case 2: Canine Transmissible Venereal Tumor (CTVT): This cancer is spread among dogs during mating or close physical contact. The cancer cells themselves are transmitted as living cells, and the immune system of the recipient dog does not always recognize them as foreign due to genetic compatibility or immune suppression.

Case 3: Contagious cancer in clams and other shellfish: Certain species of clams and mussels have been found to develop transmissible cancers that spread through water. These cancers are thought to be transmitted by cancer cells released into the environment, which are then taken up by other individuals. Environmental factors, such as pollution or stress, may play a role in the emergence of these cancers.

Summarize the conditions leading to contagious cancers: Factors such as close physical contact, genetic similarity between individuals, immune system suppression, and environmental stressors can contribute to the appearance and spread of contagious cancers. These cases are rare and typically limited to specific species under unique circumstances.

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Key Concepts

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

Contagious Cancers

Contagious cancers are rare instances where cancer cells can be transmitted from one individual to another, leading to the development of tumors in the recipient. This phenomenon has been documented in certain species, such as Tasmanian devils and dogs, where cancer cells can spread through direct contact or environmental exposure. Understanding these cases helps illustrate the unique mechanisms of cancer biology and the role of the immune system in recognizing foreign cells.

Environmental Factors

Environmental factors play a crucial role in the emergence of contagious cancers. For instance, factors such as habitat destruction, population density, and social behavior can influence the transmission of cancer cells among individuals. In species like the Tasmanian devil, close social interactions and a declining population have facilitated the spread of facial tumor disease, highlighting how ecological conditions can impact disease dynamics.

Immune System Evasion

The ability of cancer cells to evade the immune system is a key factor in the development of contagious cancers. Normally, the immune system identifies and destroys foreign cells, but certain cancer cells have developed mechanisms to avoid detection. This evasion allows them to survive and proliferate in a new host, as seen in the transmissible venereal tumor in dogs, where tumor cells can thrive despite the host's immune response.

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Related Practice

Textbook Question

The table in this problem summarizes some of the data that have been collected on mutations in the BRCA1 tumor-suppressor gene in families with a high incidence of both early-onset breast cancer and ovarian cancer.

Note the coding effect of the mutation found in kindred group 2082. This results from a single base-pair substitution. Draw the normal double-stranded DNA sequence for this codon (with the 5' and 3' ends labeled), and show the sequence of events that generated this mutation, assuming that it resulted from an uncorrected mismatch event during DNA replication.

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Textbook Question

Skin cancer carries a lifetime risk nearly equal to that of all other cancers combined. Following is a graph [modified from K. H. Kraemer (1997). Proc. Natl. Acad. Sci. (USA) 94:11 14] depicting the age of onset of skin cancers in patients with or without XP, where the cumulative percentage of skin cancer is plotted against age. The non-XP curve is based on 29,757 cancers surveyed by the National Cancer Institute, and the curve representing those with XP is based on 63 skin cancers from the Xeroderma Pigmentosum Registry.

Explain why individuals with XP show such an early age of onset.

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Textbook Question

Provide an overview of the information contained in the graph.

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Textbook Question

Researchers have identified some tumors that have no recurrent mutations or deletions in known oncogenes or tumor-suppressor genes and no detectable epigenetic alterations. However, these tumors often have large chromosomal deletions. What are some possible explanations that could account for the genetic causes behind these tumors?

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Multiple Choice

A mutation in a tumor suppressor gene causes what to happen?

True or False:Proto-oncogenes are mutated versions of oncogenes

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