Different Types of DNA


DNA testing is impacting various segments of our society, from forensics to family relationships to genealogy. There isn’t a single DNA test that is appropriate in all of these different circumstances. Depending on the answers sought and the samples available, there are actually different types of DNA tests that compare different types of DNA samples, and provide different types of DNA profiles.

DNA profiles, or DNA fingerprints, are obtained through the analysis of DNA samples, usually collected from individuals by swabbing the inside of their cheek. Each cell in our body contains DNA, and the DNA molecule for each of us is unique. So the use of DNA profiles to conclusively identify individuals has brought certainty to many questions that remained unanswered for previous generations.
The most commonly used DNA testing method today is called “short tandem repeats,” or STR. Most parts of human DNA are identical, but there are individual differences isolated in small segments of the DNA chain. These differences usually occur at the same location on the chain. STR testing looks for these differences at specific DNA sites where they typically occur. STR is an extremely accurate DNA testing method, with the chance of misidentification being one in several billion. STR testing is usually used in forensics and for DNA paternity testing.

Another testing method compares differences in the Y chromosome. Contained in the DNA’s nucleus, the Y chromosome is passed from father to son. In each paternal line, the Y chromosome is made distinctive by tiny chemical markers. These Y chromosome fingerprints allow individuals to be matched to particular patrilineal lines. Y chromosome testing is often used in ancestry studies, surname comparisons and human migration research.

Mitochondrial DNA (mtDNA), the maternal counterpart to the Y chromosome, is passed from mother to offspring (both male and female). Mitochondrial DNA is located in the cytoplasm of the cell and changes very little from generation to generation. This makes mtDNA analysis a highly effective tool for maternal lineage for hundreds of generations. MtDNA is most often used in human ancestry and origins research. It has limited uses in forensics, because mtDNA is easily contaminated.

Another interesting development in the world of DNA testing is the creating of DNA banking services. Companies providing this service guarantee the secure storage of DNA samples for future testing. This facility may be important for those who are concerned about illegitimate claims against their estate. DNA banking is also used by individuals in high-risk profession who may wish to store a DNA sample if the need for positive identification is required. If a loved one is kidnapped or goes missing, banked DNA may be helpful. As biotechnology continues to progress, it’s likely that even more different types of DNA testing and applications will emerge.