Point mutation

A point mutation is a single base substitution.^[1] It is the smallest type of mutation possible.

Illustration of three types of point mutations.

In a point mutation, either:

1. a single base nucleotide is changed for another nucleotide of the genetic material (normally DNA),^[2] or
2. a single base pair is inserted or deleted.^[3]

A nonsense mutation is a point mutation in a DNA sequence that leads to an early stop codon.^[4] This appears as a nonsense codon in the transcribed mRNA. Most of the time, the protein that is translated from this mRNA does not work.