noun, plural: nonsense mutations
Mutation is a change in the nucleotide sequence of a gene or a chromosome. When there is only one nucleotide involved, it is particularly referred to as a point mutation. Point mutation occurring in noncoding sequences often does not result in an altered amino acid sequence during translation. However, if a mutation in the promoter sequence of a gene occurs, the effect may be apparent since the expression of the gene may cause changes in the amino acid sequence, as well as the structure and function of the protein product. Point mutations may be classified based on functionality: (1) nonsense mutation, (2) missense mutation, and (3) silent mutation.
A nonsense mutation is a type of mutation resulting in a nonsense codon. The nonsense codon, as the name implies, would not code for an amino acid. A possible outcome is a protein product that is early truncated, incomplete and often nonfunctional. Genetic disease such as Duchenne muscular dystrophy is caused by a nonsense mutation in gene responsible for a specific protein, for example, dystrophin.