DNA examination involves a multi-step process, starting with sample collection and culminating in profile generation and analysis. The most common method is Polymerase Chain Reaction (PCR), a powerful technique that amplifies specific DNA regions for analysis.
DNA Extraction and Analysis
First, DNA is extracted from the sample – this might be blood, hair, skin, or other tissue. Even a tiny amount of DNA (a single nanogram) is often sufficient. MedlinePlus Genetics explains that the source of the sample can vary widely. The extracted DNA is then prepared for analysis.
Polymerase Chain Reaction (PCR)
A technique called Polymerase Chain Reaction (PCR) is crucial. PCR targets specific DNA areas, creating millions of copies. This amplification allows for reliable analysis, even with limited starting material. As noted by the North Carolina Department of Justice (ncdoj.gov), and corroborated by numerous sources like ojp.gov and ovc.ojp.gov, PCR is the cornerstone of most forensic DNA analysis.
DNA Profiling and Visualization
After PCR amplification, DNA fragments are separated based on size using techniques like capillary electrophoresis. This creates a DNA profile, visualized as a pattern of peaks or bands. These profiles are then compared to known samples or databases to identify individuals, as explained in the context of criminal justice applications by Maryville Online. The use of Short Tandem Repeats (STRs) for individual identification is a key element of this process.
Laboratory Standards
It's important to note that all DNA testing must adhere to strict quality assurance standards. Laboratories must have dedicated facilities and equipment meeting rigorous requirements, as highlighted by forensicsciencesimplified.org.
Other Techniques
While PCR is dominant, other methods exist. For instance, liquid chromatography/tandem mass spectrometry was used in the O.J. Simpson trial, as detailed in the Justice Department's report. Historically, ABO blood group analysis was used for identification before more advanced techniques became available, as discussed in ncbi.nlm.nih.gov.
