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.
