It wasn’t that long ago when the subject of DNA testing was talked about only among a select few in the scientific community. Today, you see DNA testing just about wherever you look. DNA testing is the centerpiece in several wildly popular forensic shows on television, in the dramatic conviction (or exoneration) of real-life suspects, or in high-profile celebrity paternity cases. What is DNA testing all about, how is it performed, and how is it being used? DNA testing is part of the process of DNA fingerprinting, which, simply put, is analyzing and comparing two samples of DNA. DNA fingerprinting is also called DNA profiling. The crucial fact that makes DNA testing so powerful is that no two people have the exact same DNA sequence (except identical twins).
DNA testing analyzes just a portion of a person’s DNA–the entire DNA chain is much, much too long to examine. But it is a near certainty that the segments of DNA that are tested will be unique for the individual. Early methods of DNA testing required relatively large amounts of high quality DNA material (for example, a dime-sized drop of blood). Recent advances in DNA testing methods allow the use of much smaller DNA samples.
The DNA testing method in most common use today is called “short tandem repeats,” or STR. Large sections of human DNA are identical–the individual differences (called polymorphisms) occur in small segments of the DNA chain, usually at the same location on the chain. The STR testing process looks for patterns at 13 specific DNA sites where these differences typically occur. STR is a highly accurate DNA testing method, with the chance of misidentification being one in several billion.
DNA testing and fingerprinting is used today in a wide variety of situations, and the opportunities for application are continuing to expand. One of the most popularly known uses of DNA testing is in the field of forensic science. Trace evidence containing DNA is collected at a crime scene. The DNA fingerprinting process then compares the crime scene DNA to that of suspects.
In a related field, DNA testing is now applied to the identification of human remains. DNA analysis has proven to be much more powerful than other methods of identification, especially in cases where the body has been badly damage in a fire or an accident, or if the body is decomposed.
A rapidly expanding area of DNA testing use is in paternity testing. In virtually all cases, the mother of a child is known without the need for any sort of testing. But it is possible for the relationship between father and child to be called into question. By sending a sample of their DNA (along with a sample from their supposed offspring), fathers can determine the true nature of the relationship without doubt.
Other uses of human DNA testing include matching organ donors and determination of ancestry. As the science of DNA testing continues to advance, our innate curiosity about our origins and our relationships will almost certainly combine to fuel a continued growth and expansion of the DNA testing market.