| Type of mutation | Definition |
|---|---|
| Base substitution | Changes a single DNA nucleotide |
| Transition | Base substitution in which a purine replaces a purine or a pyrimidine replaces a pyrimidine |
| Transversion | Base substitution in which a purine replaces a pyrimidine or a pyrimidine replaces a purine |
| Insertion | Addition of one or more nucleotides |
| Deletion | Deletion of one or more nucleotides |
| Frameshift mutation | Insertion or deletion that alters the reading frame of a gene |
| In-frame deletion or insertion | Deletion or insertion of a multiple of three nucleotides that does not alter the reading frame |
| Expanding nucleotide repeats | Increases the number of copies of a set of nucleotides |
| Forward mutation | Changes the wild-type phenotype to a mutant phenotype |
| Reverse mutation | Changes a mutant phenotype back to the wild-type phenotype |
| Missense mutation | Changes a sense codon into a different sense codon, resulting in the incorporation of a different amino acid in the protein |
| Nonsense mutation | Changes a sense codon into a nonsense (stop) codon, causing premature termination of translation |
| Silent mutation | Changes a sense codon into a synonymous codon, leaving the amino acid sequence of the protein unchanged |
| Neutral mutation | Changes the amino acid sequence of a protein without altering its ability to function |
| Loss-of-function mutation | Causes a complete or partial loss of function |
| Gain-of-function mutation | Causes the appearance of a new trait or function or causes the appearance of a trait in inappropriate tissue or at an inappropriate time |
| Lethal mutation | Causes premature death |
| Suppressor mutation | Suppresses the effect of an earlier mutation at a different site |
| Intragenic suppressor mutation | Suppresses the effect of an earlier mutation within the same gene |
| Intergenic suppressor mutation | Suppresses the effect of an earlier mutation in another gene |