A mutation is any change in the DNA sequence (i.e., the genome) of the cells of a particular organism. Mutations may result of 1-substitutions of one of the four nucleotide bases (Adenine, Thymine, Cytosine and Guanine) by other nucleotide bases (for example, when Adenine is replaced by Cytosine), 2-deletions, where one or more bases are removed from the DNA sequence, and 3-insertions, where one or more nucleotide bases are added to the DNA sequence. Insertions and deletions are collectively referred to as 'indels' (insertion/deletion) mutations.
