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Spontaneous mutations:

  1. The mutations that occur suddenly in nature under natural conditions are called Spontaneous mutations.
  2. Their origin is unknown.
  3. They are also called as background mutations
  4. They arise by the action of mutagenic agents present in the environment
  5. These mutagenic agents include cosmic rays, radioactive compounds, heat and naturally occurring base analogues such as caffeine.
  6. Spontaneous mutations have been reported in maize, bread moulds, bacteria, viruses, mice, man, Drosophila etc.

Induced Mutations:

  1. The mutations that can be artificially induced in the living organisms by exposing them to abnormal environment such as radiations, physical conditions (e.g. Temperature) and chemicals are called Induced Mutations.
  2. The agents which induce artificial mutations are called mutagens or mutagenic agents.
  3. Induced mutations are caused in plants by mutagenic agents which are of two types:
  4. Physical agents: X-rays, UV-rays, α, β and γ-rays.
  5. Chemical agents: Mustard gas, Ethylene amine, Colchicine, Ethyl-methyl sulphonate(EMS)
  6. It helps evolution and development of more genetic variations
Not strictly true - spontaneous mutations occur due to errors in DNA replication.  Induced mutations arise due to environmental influences and do not have to be artificially created.
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