necessarily have come from the same person. Inherent in this theory is the assumption that, if there are differences in two DNA samples, the laboratory technician will be able to detect them. Because all human beings belong to the same species, they are much more anatomically similar than difference consequently, the vast majority of DNA base pair sequences do not vary from person to person.6
However, DNA profiling is possible due to the recent discovery of techniques which allow scientists to locate regions of DNA where dramatic variations between individuals do occur. These areas of variation are known as polymorphisms.7
Two DNA typing tests have been developed, which are capable of analyzing the DNA found in criminal investigation samples or in a paternity investigation. The first test relies upon the "restriction fragment length polymorphism" (RFLP) analysis procedure. The second type of test is called the "allele specific probe analysis" and determines whether or not actual DNA characteristics are present in the sample. This is frequently referred to as "DNA amplification." The first test is more accurate than the latter, which has not yet been accepted in a court of law. However, the second test has the advantage of being able to use a small cell sample, such as a single hair follicle, and is more useful for criminal investigations, where a suspect often leaves a sample too small to be analyzed by the first method.8
In the RFLP method, after a sample of relatively pure DNA is extracted from forensic evidence, the DNA is cut into segments with a mixture of restriction enzymes. An electric current is then sent through a gel containing the DNA fragments. The smaller fragments move more quickly through the gel, so that the fragments are sorted by length. The fragments are then placed on a nylon membrane and the Restriction Fragment Length Polymorphism (RFLP) probe is used to radioactively mark the DNA strands. ...