PCR, or polymerase chain reaction, is used to detect disease in its early stages by detecting the pathogen after replicating the DNA multiple times. Since replication of DNA is involved, Sanger’s method is used. A target DNA segment is amplified using the Sanger method in order to precisely ascertain the DNA sequence. Simply put, the integration of ddNTPs in the reaction mechanism serves to stop the synthesis of an expanding DNA strand, leaving behind DNA fragments that have partially duplicated.