Mutagens and teratogens are chemical, physical or biological agents that are lethal to individuals. While mutagens alter the DNA sequence of an individual, teratogens cause harmful effects on the developing foetus during pregnancy. Read this article to know the differences between mutagen and teratogen.

Table of Contents

What Is Mutagen?

Mutagens are physical or chemical agents that alter the DNA sequence of an individual and cause a permanent change in their genetic makeup. This increases the frequency of mutation in an organism. If these mutations cause cancer in an organism, they are referred to as carcinogens. However, all mutagens are not always carcinogens. The process of modification of DNA by mutagens is known as mutagenesis.

Types of Mutagen

1. Physical Mutagens: Ionising radiations such as gamma rays, X-rays and alpha particles break the DNA strands. UV rays that are above the wavelength of 260 nm produce pyrimidine dimers which affect the replication of DNA.
2. DNA Reactive Chemicals: Highly reactive species such as superoxides, hydrogen peroxide and oxygen free radicals are generated by normal cellular processes that can create base adducts, DNA crosslinks and breakage. Other DNA reactive chemicals include deaminating agents (that deaminates bases), polycyclic aromatic hydrocarbons (PAH), alkylating agents, aromatic amines, alkaloids from plants, benzene, bromine and sodium azide.
3. Base Analogs: Base analogues such as 5-bromouracil and 2-aminopurine can substitute at the place of nitrogenous bases in the DNA strand and cause transition mutations.
4. Intercalating Agents: The agents that can insert themselves in between DNA bases and cause frameshift mutations are called intercalating agents. Examples include proflavine and ethidium bromide.
5. Metals: Metals such as arsenic, cadmium, nickel and chromium are often associated with reactive oxygen species (ROS) and can cause alterations in DNA.
6. Biological Agents: Transposons can insert themselves into the chromosomal DNA and hinder the process of replication. Viral DNA also gets incorporated into the genome and disrupts genetic functioning.

What Is Teratogen?

An agent that causes physical and functional defects in the embryo after the mother is exposed to those agents is known as teratogens. Most common examples of teratogens include mercury, retinol, alcohol, thalidomide, lead and polychlorinated biphenyls (PCBs). The most common causes of teratogenesis include taking drugs during pregnancy, exposure to environmental toxins, alcohol, lack of nutrients and genetic disorders.

Teratogens can be found anywhere in our surroundings, be it your home or workplace. The effect of teratogen depends on the type of agent, the dose given and the duration of exposure. The first half of a woman’s pregnancy is the most vulnerable. The severity of the defect caused by the teratogen also depends on the genetic susceptibility of the mother and the foetus.

Teratogens affect the behavioural and emotional development of the child, cause physical malformations and can also cause preterm labour, spontaneous abortions or miscarriages. Scientists have divided teratogens into four types:

1. Physical: Physical teratogens include ionising radiations such as X-rays and gamma rays that cause hypothermia (elevated body temperature) that can lead to CNS malformations, microcephaly, defects in the eye and limb development in the foetus. Saunas, hot tubs and infections are also physical agents that cause hypothermia.

1. Chemical: Consumption of drugs and chemicals such as alcohol, cocaine, retinoids, and thalidomide can cause physical malformations such as absence, shortened or extra limbs, heart defects and various nutritional deficiencies.
2. Maternal Conditions: Metabolic conditions in the mother, such as thyroid, diabetes, and malnutrition, can hinder the process of producing energy from food and therefore affect the development and functioning of the foetus.
3. Infectious: Infectious agents such as those causing rubella, herpes, and syphilis make direct contact with the mother’s body fluids and cause congenital disorders in the developing foetus.

Mutagen vs Teratogen

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