[The amplification of nucleotide sequences by PCR and the new technics for molecular diagnosis].

The polymerase chain reaction (PCR) is a method for selective amplification of DNA or RNA segments of up to 2 kilobase pairs (kb) or more in length. Repeated cycles of enzymatic primer extension in opposite directions are performed using synthetic oligonucleotides flanking the sequences of interest and the heat-stable DNA polymerase from the archaebacterium Thermus aquaticus (Taq polymerase). The reaction is simple, fast and extremely sensitive, and the DNA or RNA content of a single cell is sufficient to detect a specific sequence. This method has proved useful in simplifying complex analytical protocols in basic and applied molecular biology.