Mutagens: Definition, Types, Effects

Mutagens are mutation-causing agents which are responsible for the alteration of genetic material in individual organisms. Mutation can be of any origin, be it physical, chemical, or biological. Mutagens are responsible for the increase in the frequency of mutations above the level of the natural background. While not all mutations are potentially harmful, some genetic variations caused by mutagens may damage or harm cells and can also cause certain diseases.

Some examples of mutagens are heat, ionizing radiations, alkylating agents, intercalating agents, transposons, etc. 

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Keyterms: Mutagens, Genetic material, Heat, Ionizing radiations, Alkylating agents, Intercalating agents, Transposons, DNA, Tumors, Cell, Individual organisms

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Discovery of Mutagens

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Carcinogens are the first-ever mutagens to be discovered about 2,000 years ago, even before the discovery of chromosomes and DNA. The discovery of tumors was solely described by the effects caused and there was no knowledge of mutagens at that time. It was in the eighteenth century that scientists started discovering and demonstrating the different types of mutagen and mutagenic effects in detail.

In recorded history, there is a well-documented case of a particular ‘wasting disease’ caused in minors. Wasting disease was later identified as lung cancer and was caused due to the exposure of mutagens in the poor conditions of mines with less ventilation. The mutagen causing this disease was found to be radon, which is colorless, odorless, tasteless, and high in radioactivity.

Discovery of Mutagens

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Types of Mutagens

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Based on their nature, mutagens are classified into three types. They are, namely, physical, chemical, and biological mutagens.

• Physical Mutagens: Physical Mutagens or physical mutagenic agents are of physical origin and include ionizing radiations (X -rays, gamma rays, alpha particles), ultraviolet(UV) radiations, and radioactive decay(decay heat). In general, heat and radiation are the best examples of physical mutagens.
• Chemical Mutagens: Chemical Mutagens or chemical mutagenic agents are of chemical origin and include base analogs, DNA reactive chemicals, alkylating agents, intercalating agents, and some metals such as arsenic, cadmium, chromium, nickel, and their compounds.
• Biological Mutagens: Biological Mutagens or biological mutagenic agents are of biological origin and include transposons, viruses, and certain bacteria such as Helicobacter pylori.

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Effects of Mutagens

Some of the effects of Mutagens are listed below as follows,

• Mutation brings about a change or alteration of the existing expression of a specific genotype or phenotype. The effect of mutagen in one individual organism will not be similar to the effect of the same mutagen on another organism. It may vary depending on the genetic constitution and expression.
•  In certain instances, where a mutagen affects a non-coding DNA, no visible change is found on it, such mutations are called silent mutations. In other instances, where there are more noticeable effects caused by mutagens, such mutations can harm or undermine the DNA of the organism, both directly and indirectly. Hence, the mutagens are considered genotoxic. 
• Carcinogens or cancer-causing agents are a class of mutagens that affects the individual organism’s DNA and brings about genetic mutations causing cancer. Mutagens include carcinogens that alter the genetic material while it is not necessary that all carcinogens are mutagens. Examples include X-rays, ultraviolet radiations, aflatoxins, retroviruses, etc.

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Protection Against Mutagens

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Some of the key measures that can be taken up for protection against Mutagens are listed below for your reference,

• To protect against physical mutagens, it is best to limit or avoid exposure to heat and radiations of high energies, especially that of tobacco smoke and ultraviolet radiations of which the individual is more vulnerable to be exposed.
• Antioxidants, a pivotal group of anticarcinogenic compounds, help remove Reactive Oxygen Species(ROS) and other chemicals that cause harm to an individual organism. Examples are Vitamin A, Vitamin C, Vitamin E, polyphenols, etc.
• There are also other chemicals that have anticarcinogenic properties and can prevent cancer and reduce mutagenic extent to some certain extent. Examples are sulforaphane, which is effective against prostate cancer, and others include indole-3-carbinol, resveratrol, etc.

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Role of Mutagens in Anti-cancer Therapy

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• Certain mutagens are used in anti-cancer therapies due to them being highly harmful and toxic to proliferating cancer cells, hence helpful in the destruction of cancer cells.
• In chemotherapy, alkylating agents and intercalating agents are used for treatments. Examples of alkylating agents include cyclophosphamic and cis-platin, while that of intercalating agents include daunorubicin and doxorubicin.
• In radiation therapy, ionizing radiation is used for the treatments.
• It is the same property of mutagens being carcinogenic, which is used in anticancer therapies. A collective combination of mutagens, such as a combination of ionizing radiations and intercalating agents, can collectively work together in destroying the DNA of the cancer cells and thus inhibiting their proliferation.
• However, these anti-cancer therapies are prone to some disadvantages, as these mutagens can affect non-cancerous cells, hence causing side effects such as nausea and hair loss.

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Key Terms

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• Mutagens: Mutagens are mutation-causing agents which are responsible for the alteration of genetic material in individual organisms. Examples of mutagens are heat, ionizing radiations, alkylating agents, intercalating agents, transposons, etc.
• Mutation: Mutation is the alteration of base sequence in the genetic material resulting in genetic variations.
• Carcinogens: Carcinogens or cancer-causing agents are a class of mutagens that affects the individual organism’s DNA and brings about genetic mutations causing cancer. Examples are X-rays, ultraviolet radiations, aflatoxins, retroviruses, etc.
• Transposons: Transposons or transposable elements are DNA sequences that are repetitive and can transpose within a genome, that is moving from a particular location of the genome to another.
• Base Analogs: Base analogs are chemicals capable of substituting normal bases in DNA and can cause transition mutations. Examples are 5-bromouracil, 2-aminopurine, etc.
• Intercalating Agents: Intercalating agents are chemicals that are inserted between the successive bases of the DNA during intercalation. Examples are ethidium bromide, cyclophosphamic, proflavin, cis-platin, etc.
• Intercalation: Intercalation is the molecular insertion between the planar bases of the DNA and is used for analyzing the DNA.
• Mutation Breeding: Mutation breeding is the process of artificially inducing mutations with the use of certain chemicals and high-energy radiations to create genetic mutants with the desired traits. Resistance to yellow mosaic virus and powdery mildew in mung beans is an example of mutation breeding.

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