In 1983, Kary Mullis and members of the human genetics team at Cetus Corporation developed a genetic replication technique called polymerase chain reaction (PCR). After several years of fine-tuning the process, PCR became the most popular DNA replication technique by the 1990s. Kary Mullis was awarded the Nobel Prize in Chemistry for this work in 1993.
The popularity of PCR is based on both the sample size and the processing time it requires. DNA testing utilizing PCR can be performed in a matter of hours with a very small DNA sample.
In PCR, scientists isolate a small amount of DNA (an amount easily obtained from a buccal swab). They then copy regions on the DNA many times to establish large quantities of DNA fragments from the copied regions. PCR can be used to copy any region of DNA.
For PCR use in paternity testing, scientists isolate a small amount of DNA and copy many specific DNA fragments (or loci) that help identify and differentiate people. Fragments from one individual are compared to fragments from other individuals, as done in RFLP, and relationships are determined based on the similarities and differences between the DNA fragments or genetic profiles.