There are several different types of mutation that can occur in DNA:
Single Nucleotide Polymorphisms (SNPs) A single nucleotide polymorphism mutation is where one base is switch for another. These are common within species, where they convey variation between species.
Point Mutation The switching of a single nucleotide for another, of one of two types: Transversion - the switching of a pyrimidine for a purine, or vice verse Transition - the substitution of bases within the purine / pyrimidine classes of nucleotide, while
Nonsense Point mutation resulting in the premature coding of a STOP codon, almost always leading to a dysfunctional protein product.
Missense A mutation arising from changing a single nucleotide, switching the amino acid coded for
Frameshift The insertion or deletion of a nucleotide, leading to the reading frame being shifted by a nucleotide - almost always resulting in a dysfunctional protein being produced.
Slip-strand mispairing Type of mutation, typically changing the number of repeat regions, due to the dissociation and re-association of the DNA polymerase during replication.
Insertion The insertion of a nucleotide, causing a frameshift mutation.
Deletion The removal of a nucleotide, causing a frameshift mutation.
Transposon A mobile genetic element, able to disrupt genes and thus inactivate them.
Homologous Recombination A frequent method of increasing genetic variation within a species, by exchanging DNA between chromosomal arms (in the case of crossing-over). This occurs especially so during meiosis, forming gametes.