* Addition or subtraction: When the gene mutation occurs by the addition or subtraction of bases, it modifies the genetic code and defines a new sequence of bases. As a result, this new sequence can modify the type of amino acid present in the protein chain, changing the function of protein or inactivating the phenotypic expression.
* Replacement: The gene mutation by replacing happens by the exchange of a base fertilization purina (adenine and guanine) by another purina or a pyrimidine (cytosine and thymine) by another pyrimidine.