Info about Dna Testing
DNA Testing - Uses and Techniques
DNA or deoxyribonucleic acid is the biological molecule that determines structure, function and development in all living organisms. This molecule is present in every cell of the body. Developments in genetics, biotechnology and related sciences have made it possible to do DNA testing and determine the genetic profile of organisms, including human beings.
In forensics, DNA testing allows the identification of an individual based on his or her genetic make-up. This is the reason why the process is also called DNA typing, genetic fingerprinting, or DNA profiling. It has been determined from research studies that about 99.9% of the human DNA is exactly the same among persons. Human DNA contains about 3 billion base pairs. Therefore, that remaining 0.1 percent is still enough to make a distinction between persons.
The principle behind DNA testing is that it finds repeat sequences that vary highly among unrelated individuals. These repeat sequences are called Variable Number Tandem Repeats (VNTRs). The process is highly useful in legal cases where the identities of the persons involved are of utmost relevance. Such cases include paternity, rape cases or even fires that result to mass deaths.
Although all cells of the body contain DNA, samples gathered are usually from the mouth, through the use of buccal swabs. Other sources of specimens are blood, saliva, hair and semen. The “reference” sample which is simply a person’s own DNA is analyzed using various techniques. Comparison is then made between the reference sample and the test sample to find out if there is a genetic match. In forensic cases, if a match is found between the reference sample from a suspect and evidence from the crime scene, the probability becomes higher that the crime is indeed done by the suspect.
There are several methods used in DNA testing. In the RFLP (restriction fragment length polymorphisms) technique, the DNA is digested by restriction enzymes and the fragments are then subjected to Southern blot analysis. Unfortunately, this technique is arduous and has highly variable results. PCR (polymerase chain reactions) analysis is now at the forefront of DNA testing. In PCR, a specific fragment is first amplified or replicated several times using primers and Tac (Thermophilus aquaticus) DNA polymerase. STR (short tandem repeat) analysis involves determining the tandem repeats in a person’s DNA.
DNA testing has many uses. Aside from identification of individuals or determination of blood relationships, DNA testing is useful in detecting infectious organisms. For instance, there are PCR-based assays to detect malarial and dengue infection.
The process is also now used to predict the risk of certain familial diseases. In oncology, DNA testing is used to determine the lineage of cancer lines. It is also used in evolutionary biology, wherein the presence of certain DNA sequences in populations provides a clue on human ancestry.
DNA testing has been in existence for a number of years. Now, the process is available for consumers through commercially marketed test kits or laboratory tests. Down the line, there will be improvements in the techniques and uses as scientists continue exploring the fascinating world of DNA.