The DNA as hereditary material transmitted with great fidelity to the next generations. Although DNA polymerases synthesize DNA with a very low error rate and have mechanisms to repair their errors, alterations do occasionally occur. These changes produced in DNA replication are mutations.
Hugo de Vries, in addition to being one of those who rediscovered Mendel's laws in 1900, was the first to use the term mutation when studying the sudden changes that appeared in the offspring of some Oenothera lamarkiana plants. He defined mutation as "any heritable change in hereditary material that cannot be explained by segregation or recombination."
This definition changed when it became known that the hereditary material is DNA and the double helix structure of DNA (Watson and Crick, 1953). Mutation was defined as any change in the nucleotide sequence of DNA.
Mutations can be classified according to several criteria:
- According to the type of cells that are affected:
- Somatic: They are not inherited, since they are only transmitted to cells that originate from mitosis. They are the majority.
- Germ: They affect the gametes or the cells that produce them, and are transmitted to the offspring.
- According to the cause that originated them:
- Natural or spontaneous.
- Induced by mutagens. The causes of these mutations will be discussed in another section.
- According to the effects it produces in the body:
- Beneficial. Some mutations (less than 1%) improve the function of the protein they encode.
- Harmful or deleterious.
- Neutral. They are silent, they neither benefit nor harm.