Schematic representation of mutation detection using solid-phase capturable dideoxynucleotide terminators and MALDI-TOF MS. Wild-type DNA has the same sequence for both copies, from which a single peak is produced at every position in the mass spectrum that corresponds to the nucleotide existing at that position in the DNA template (left). However, mutant DNA with an insertion or deletion (insertion shown here as an example) in one copy can have two different bases coexisting at the same sequence position in the two alleles. This leads to the formation of two distinct mass peaks at each position in the mass spectrum (right). By calculating the corresponding mass differences, the sequences of both alleles can be simultaneously read and the mutation site can be accurately characterized.