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  1. Difference between mutagen and carcinogen
  2. Difference between mutagen and teratogen
  3. Difference between carcinogen mutagen and oncogene

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  1. The physical or chemical agents causing mutations are called mutagens.
  2. Examples:
  • Radiations like UV light, X-rays, γ-rays, etc.
  • Nitrous oxide
  • Alkylating agents like dimethyl sulphate (DMS)
  • Base analogues.


  1. The physical, chemical or biological agents that cause cancerous growth in the body are called carcinogens.
  2. Examples:
  • Ionizing radiations —→ UV rays, X-rays, γ-rays
  • Chemical agents  —→  Cigarette smoke, hydrocarbons
  • Physical agents  —→ Heat
  • Biological agents  —→ Epstein-Barr virus


  1. The drug or agent that causes foetal abnormalities of both form and function is called a Teratogen.
  2. Teratogens hinder embryogenesis by disturbing one or more developmental processes.
  3. It may lead to over-development or underdevelopment of organs, lack of cell differentiation.
  4. Examples:
  • LSD  —→ Chromosomal and foetal abnormalities
  • Ethanol  —→ Foetal alcohol syndrome  —→ Mental retardation, facial abnormalities
  • Smoking  —→ Poor foetal growth, pre-mature delivery
  • Radiation  —→ CNS defects, Malformations of eye
  • Antibiotics  —→ Streptomycin  —→ Loss of hearing


  1. The inactive cancer causing genes present in every individual are called Proto-oncogenes or cellular oncogenes.
  2. In normal state, the oncogene is repressed.
  3. Carcinogens or mutagens change or activate these proto-oncogenes by causing change in the DNA.
  4. These gene mutations cause loss of normal control mechanism and cells undergo abnormal division.
  5. The translation products of  oncogenes are oncoproteins which are associated with cancerous growth.
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