Principles of Inheritance and Variation

A mutation that arises from a change in a single base pair of DNA is called a point mutation.
The classical example is sickle-cell anaemia, in which a single base substitution (GAG to GUG in the codon for the sixth amino acid of the β-globin chain) replaces glutamic acid by valine.
Deletions and insertions of base pairs cause frame-shift mutations, and duplication is a chromosomal change.
Hence a point mutation involves a change in a single base pair.