How Dna Testing Is Done

The era of DNA testing started in the 1980s, when investigators were finally able to perform almost unbelievable feats of identification. With technology available in present days, it is possible for a single person to be differentiated from all the people that have ever lived using DNA from a single hair root. Through DNA testing, DNA profiles are created, making it an an indispensable tool for positional cloning, a technique by which a previously unknown gene is identified by finding associations or links between DNA markers and the inheritance of a disease.

Compared to other serological methods such as blood typing and HLA analysis, DNA testing has a number of real advantages. The first one is the unmatched discriminatory potential, as DNA testing can routinely provide exclusion probabilities on the order of one in billions, whereas other methods are much more limited. The second advantage is the exquisite sensitivity. DNA testing can be done just by using a few hairs, DNA can be amplified so even smaller sample size are useful. The third advantage is that it can be applied to any body tissue, not just blood. DNA testing can be done on samples as hairs, semen, urine and saliva. And last but not least, DNA is stable in comparison to proteins. DNA testing can therefore often be performed on samples that have been exposed to detergents, acids and bases, gasoline, salt, and bacterial contamination. DNA doesn't degrade over time, so reliable information can be obtained even from samples that are decades old.

Nevertheless, there are some concerns surround DNA testing, based on allele frequencies in certain populations. These frequencies are used in calculation of calculating probability of identification. The problem was that the odds of a random match may be higher than stated because the database used was inappropriate for the subpopulation of people containing the suspect.

There are two types of DNA testing methods - Single locus DNA fingerprinting and Multilocus DNA fingerprinting. Every method has certain advantages over the other in specific situations, so one must be aware of them to be able to make the right decision as to which one should be used in a given case. For example, single locus but not multilocus methods are useful when the DNA is degraded and for mixed (i.e. victim and pertetrator) samples. On the other side, multilocus fingerprinting generally provides more data per sample than single locus fingerprints.