Difference Between Spontaneous and Induced Mutation

Key Difference – Spontaneous vs Induced Mutation
 

Mutations are referred to as changes in the DNA sequence of an organism that would result in a phenotypic change, either beneficial or harmful. Mutations can also be silent mutations that will not affect the phenotype. Mutations have contributed much towards the evolution of species. Mutations are mainly divided into two main categories based on the causation of the mutation. They are Spontaneous Mutations and Induced Mutations. Spontaneous Mutations are the mutations that are unpredictable and occur due to errors in replication of DNA. Induced mutations are the mutations that are caused by known physical, chemical or biological agents. These mutations are caused due to exposure to these agents, resulting in a change in DNA sequences. The key difference between spontaneous and induced mutations is the causative agents of these mutations. Thus, spontaneous mutations are unpredictable changes in the DNA caused due to errors in replication, whereas, induced mutations are caused by physical, chemical or biological agents. 

CONTENTS

1. Overview and Key Difference
2. What is Spontaneous Mutation
3. What is Induced Mutation
4. Similarities Between Spontaneous and Induced Mutation
5. Side by Side Comparison – Spontaneous vs Induced Mutation in Tabular Form
6. Summary

What is Spontaneous Mutation?

Spontaneous mutations are caused by the non – repaired errors that take place during the DNA replication process. These errors can either lead to transitions between nucleotide bases or transversions between bases. The transition of bases results when a purine (adenine) is replaced by another purine base (guanine) or a pyrimidine base (thymine) is replaced by another pyrimidine (cytosine). Transversion of bases refers to the replacement of purine base by a pyrimidine base and vice versa. Spontaneous mutations are caused mainly due to chemical mutagens such as intercalating agents, alkylate guanidine, nitric oxide and radiation types such as ionizing and non-ionizing radiation, etc. The rate of a spontaneous mutation varies rapidly, and diseases caused due to spontaneous mutations mainly arise from chromosomal aberrations caused by the mutation.

In spontaneous mutations, the source of the mutation is not predictable or not known. Therefore, determining the cause of the mutation is not possible. The most discussed example of spontaneous mutation is the occurrence of sickle cell anaemia. Over generations, the cause of the mutation leading to sickle cell anaemia is not known. Sickle cell anaemia is also associated with malaria resistance, where subjects with sickle cell anaemia positive, do not incur malaria.

What is an Induced Mutation?

Induced mutations are mutations caused by specific known agents. Therefore, in induced mutations, the cause of the mutation can be predicted. These mutations also result in transitions and transversions of bases. The occurrence of the mutation depends on the dose of the mutation and the frequency of direct or indirect exposure to the mutagen. Therefore, individuals who are exposed to mutagens frequently are more prone to mutations. Thus, workers who are dealing with harmful chemicals and heavy metals, radiation types such as x – rays are more prone to induced mutations.

These type of mutations can be prevented by creating awareness on mutagens are by using proper safety precautions when handling the mutagens. The common examples of induced mutations include skin cancers due to continuous exposure to radiation and kidney diseases due to exposure to heavy metals.

What are the Similarities Between Spontaneous and Induced Mutation?

• Both Spontaneous and Induced mutations result in changes in the DNA sequences caused by transitions or transversions.
• Both Spontaneous and Induced mutations are caused by mutagens such as chemical, physical or biological agents.
• Both Spontaneous and Induced mutations may result in harmful effects, beneficial effects or may not have any effect based on the impact of the mutation on the DNA sequence.
• In both Spontaneous and Induced mutations, the dose and the frequency of the mutagen plays an important role.
• Both Spontaneous and Induced mutations can be detected by using molecular techniques such as polymerase chain reaction methods, etc.

What is the Difference Between Spontaneous and Induced Mutation?

Summary – Spontaneous vs Induced Mutation

Mutations are changes in DNA sequences that can be heritable if they occur in sex chromosomes. Causative agents of mutations are known as mutagens, and they can be chemical, physical or biological. Depending on the predictability of the mutation, they are divided as spontaneous and induced. Spontaneous mutations are mutations that occur spontaneously and the source of the mutagen in unknown. Induced mutations are caused by mutagens in which the source is known. This is the difference between spontaneous and induced mutation.

Reference:

1.Genes and Mutations – Spontaneous and Induced Mutations. Available here
2.Lodish, Harvey. “Mutations: Types and Causes.” Molecular Cell Biology. 4th edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here

Image Courtesy:

1.’Skin cancer waxy lump’ By  National Institutes of Health (Public Domain) via Commons Wikimedia