Typical design of a circularisable padlock probe. Design and components of a typical padlock probe as exemplified by the Ca-Y132H probe specific for the Y132H amino acid substitution. The probe comprises (i) a 5'-phosphorylated end; (ii) a "backbone" containing binding sites for the RCA primers (RCA primer 1 and 2, respectively) designated by bold upper case letters) as well as the non-specific linker regions (designated by bold lower case letters) and (iii) a 3'-end. The 5'- and 3'-ends of the probe are complementary to the 5' and 3' termini of the target sequence in reverse, in this example, to the C. albicans sequence (GenBank accession no. AF153844). Abbreviations: 5'-P, 5'-phosphorylated binding arm; 3'-, 3' binding arm.