DNA (an acronym for deoxyribonucleic acid) is
|“||a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses.||”|
|“||a molecule found in most cells of all people, animals, plants and other organisms. Variations in the DNA sequence enable the distinction between individuals.||”|
The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Genes make up five percent of the human genome. The other 95 percent are non-coding sequences, (which used to be called junk DNA). In non-coding regions there are identical repeat sequences of DNA, which can be repeated anywhere from one to thirty times in a row. These regions are called variable number tandem repeats (VNTRs). The number of tandem repeats at specific places (called loci) on chromosomes varies between individuals. For any given VNTR loci in an individual's DNA, there will be a certain number of repeats. The higher the number of loci that are analyzed, the smaller the probability to find two unrelated individuals with the same DNA profile.
DNA profiling Edit
DNA profiling determines the number of VNTR repeats at a number of distinctive loci and uses it to create an individual's DNA profile. The main steps to create a DNA profile are: isolate the DNA (from a sample such as blood, saliva, hair, semen, or tissue), cut the DNA up into shorter fragments containing known VNTR areas, sort the DNA fragments by size, and compare the DNA fragments in different samples.
The benefit of using DNA as a biometric identifier is the level of accuracy offered: the chance of two individuals sharing the same DNA profile is less than one in a hundred billion with 26 different bands studied.
- ↑ Interpol Handbook on DNA Data Exchange and Practice, Glossary, at 104.