The PCR Lab Test in Forensics and Medicine
An Overview of the PCR Lab Test
The PCR lab test (polymerase chain reaction) was developed to overcome the obstacle of quickly replicating DNA for research use.
Developed in the 1980s, the PCR lab test is widely applied in medicine, from identifying new viruses to testing for bacterial illness. An alternate application is criminology, where it is used to help find potential perpetrators.
Polymerase is an enzyme which functions mainly to replicate a portion of the DNA before the primers disconnect. Primers are just pairs of simple proteins where a sequence begins: commonly “A” pairs with “T”, and “G” pairs with “C.” Since these small segments of DNA have such a low volume quantity, the pairings need to be amplified to get an adequate sample.
Forensics
Since an individual has so many unique base pairs, the likelihood of a false-positive result in criminal cases or paternity cases is very small: similar to the the odds of an individual winning the lottery several times over. Post-conviction DNA testing has impacted many lives in Illinois: executions were halted for death-row prisoners, and a few were granted clemency. Public opinion polling says DNA evidence is a main factor influencing the outcome of criminal cases if such data is available. And like television viewers may have seen on Maury; exonerate fathers in paternity testing.
Medical Application
In addition to its criminal component, the PCR lab test has an immediate impact in genetic typing for tissue donation and transplantation. If the sequences are a partial match, then the organ system has less of a chance of being rejected by the donation recipient. A more advanced version of PCR is RT-PCR, which can be used to measure viral load in HIV-positive patients. Similar pathogen-specific PCR processes have already been completed or are in the product pipeline.
Ancestry Impact
From an evolutionary perspective, certain sequences (loci) help identify biological ancestors. This helps researchers investigate the transition between mankind’s earliest specimens. Even the smallest amounts of tissue are used to map a genetic hierarchy and compare human/chimp similarity. Most recent evidence indicates that humans share up to 99 percent of the DNA with the model chimpanzee.
Future
The trajectory for DNA research with PCR looks bright. Many diseases have a genetic component, and PCR fits well with tailoring treatments to a patient’s genetic code. The new process is called pharmacogenomics. In 2007, the genetics budget for the National Cancer Institute was allotted 1.4% of total endowment. As the endowment increases in 2011, the allotment will more than double. The institute is using that new funding to genotype the most common 20 types of cancers.
Closely examining these amplified sequences is arguably one of the greatest science strides of the 20th century. Expounding upon this discovery is propelling medical science through the 21st century. All of this progress from a likely man, Kary Mullis, future Nobel Laureate. He brainstormed the process while going for a drive down the Pacific Coast Highway.
References
“Genome.gov | PCR Fact Sheet.” Genome.gov | National Human Genome Research Institute (NHGRI) - Homepage.
“Polymerase Chain Reaction.” Plattsburgh State Faculty and Research Web Sites.
“Polymerase Chain Reaction (PCR): Biology Animation Library.” Dolan DNA Learning Center.
