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Uses of PCR in Forensics

Polymerase chain reaction (PCR), invented in the early 1980s, is a process that increases the amount of DNA present in a sample to create an adequate sample size. It allows trace amounts of DNA found at a crime scene to be magnified into tenable data to pursue suspects or identify victims.

  1. Amplification

    • PCR amplifies the DNA nucleotide bonds on a DNA sequence, which is helpful in forensics because everyone's DNA is different and the PCR process helps to determine the unique DNA "fingerprint" of victims or suspects. These genetic sequences are called variable number of tandem repeats (VNTR).

    Reliability

    • The more unique nucleotide sequences that can be determined and amplified, the greater the confidence level of identifying a suspect or victim becomes. For example, the use of 5-10 VNTRs means that the confidence level is one in 10 billion.

    DNA Sources

    • PCR is useful for forensics because DNA is present in most human biological matter. PCR can use DNA found from saliva, blood, hair, other bodily fluids, and even dead skin cells that often collect underneath fingernails. The PCR process means that even though there may be little DNA on these sources, VNTR sites can be amplified to identify a person's unique DNA signature.

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