Sequence-specific amplification

One of the properties of the short synthetic pieces of DNA
(oligonucleotides) used as primers in PCR is their sequence
specificity. This can be exploited to design PCR primers that
only generate a product when they are perfectly matched to
their target sequence. Conversely, a mismatch in the region of
sequence where the primer binds, prevents PCR amplification
from proceeding. In this way, an assay can be designed to
detect the presence or absence of specific known mutations.
This approach (known as ‘ARMS’ or Amplification Refractory
Mutation System) is often used to detect common cystic fibrosis
mutations and certain mutations involved in familial breast
cancer.