A mutation is an alteration in the DNA sequence of an organism, virus, or extrachromosomal DNA

. Mutations can occur during DNA or viral replication, mitosis, or meiosis and may result from exposure to mutagens or viral infection

. A mutation can be passed to offspring if it occurs in germline cells (eggs and sperm) but not if it occurs in somatic cells (body cells)

. Mutations are a main cause of diversity among organisms

. Mutations can be changes within genes, called point mutations, or mutations that span more than one gene, called chromosomal mutations

. Types of mutations:

• Point Mutations Point mutations are changes to single base pairs and may substitute an incorrect amino acid in the corresponding position in the encoded protein

• Chromosomal Mutations Chromosomal mutations affect the structure, function, and inheritance of entire DNA molecules

. Examples include large-scale deletions, duplications, inversions, and translocations. Inversions and translocations are functionally normal unless a break occurs within a gene.

• Substitution Substitutions exchange one base for another

• Nonsynonymous Mutation These mutations lead to either the production of a different protein or the premature termination of a protein

• Synonymous Mutations Synonymous mutations do not change an amino acid sequence but occur only in sequences that code for amino acids

• Insertion Insertions add one or a few nucleotides

• Deletion Deletions remove one or a few nucleotides