Induced Mutations

Induced mutations: Mutations can be induced by exposing organisms (or cells) to a variety of treatments. Some of the most common are:

Radiation- One of the first known mutagens, radiation is a potent inducer of mutations. Different types of radiation cause different types of genetic changes. Ultraviolet (UV) radiation causes point mutations. X-rays can cause breaks in the DNA double-helix and lead to translocations, inversions and other types of chromosome damage. Exposure to the UV rays in sunlight has been linked to skin cancer. Note that the DNA damaging properties of radiation have been utilized in several different radiation-based cancer treatments.

Shown below is a type of mutation that is caused by ultraviolet radiation. In this example, the bombardment of the DNA double-helix by UV rays causes two bases to join together. This alters the structure of the DNA and can lead to permanent changes if not repaired.

Another type of radiation is the energy emitted by naturally occuring radioactive elements (like radon and uranium) or man-made sources like those found (and created) in nuclear reactors.  Radiation of this type comes in different types and can cause different types of damage to cells and tissues.  Radiation can directly damage DNA or can cause the formation of chemicals (i.e. reactive oxygen species or ROS) that can then damage DNA or other cell components.

Exposure to radiation from radioactive materials has been well documented.  Analyses of survivors of the atomic bombs dropped on Japan during World War II showed large increases in leukemias shortly after the exposure and then increases in other cancer types over the following decades.⁽¹⁾

Dangerous amounts of radioactive materials have also been accidentally released from nuclear power plants. Radiation exposure due to the accidental release of radioactive materials from the Chernobyl nuclear reactor have been associated with increases in thyroid cancer and other malignant cancers.⁽²⁾

Medical imaging machinery (like X-ray machines and CT scanners) also expose patients to radiation.  The amounts used for any single test are not thought to cause siginificant amounts of cancer, but the long term impact of many tests over a period of years is not clear.⁽³⁾  Likewise, the exposure of airplane passengers to full-body scans at airports is not thought to pose a risk of cancer.⁽⁴⁾  Passengers flying in planes are also exposed to radiation from space, but at a low level and is not thought to pose a cancer risk, even for flight crew members.⁽⁴⁾⁽⁵⁾

Chemical mutagens- Many different chemicals are known to cause mutations. These chemicals exert their effect by binding to DNA or the building blocks of DNA and interfering with the replication or transcription processes. Some examples of potent mutagens are benzo-a-pyrene, a chemical found in cigarette smoke, and aflatoxin, a mutagen most often found on improperly stored agricultural products.

Chronic inflammation- Chronic inflammation can lead to DNA damage due to the production of mutagenic chemicals by the cells of the immune system. An example would be the long-term inflammation caused by infection with the hepatitis virus. Learn more about viruses and cancer.

Oxygen Radicals- During the capture of energy from food, which occurs in our mitochondria, chemicals may be generated which are very reactive and are capable of damaging cell membranes and DNA itself. These reactive oxygen intermediates (ROI) may also be generated by exposure of cells to radiation, as shown below.

The mutagenic activity of ROI is associated with the development of cancer as well as the activities of several anticancer treatments, including radiation and chemotherapy. ^{(6) (7) (8)}

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