What is DNA?
Deoxyribonucleic acid (DNA) is a long molecule, found in the cellular nuclei of living organisms. Since 1954, scientists have recognized that the chemical structure of an individual’s DNA encodes information about that individual’s inherited characteristics. The present limits on genetic science mean that a direct analysis of a person’s DNA will yield only limited information about individual characteristics, although some research suggests that investigators may in the future be able to discern specific physical traits such as hair, eye and skin color from forensic samples. Rather, the current utility of DNA analysis to the criminal justice system arises from the comparison of DNA from two sources, such as DNA from a crime scene and DNA from a suspect, to determine the relationship between those sources. Traditionally, the identification of a person has required the observation of that person’s entire body or of localized special characteristics such as fingerprints, blood group or hair type. By contrast, DNA analysis allows identification by reference to the information contained in any human nucleic cell, irrespective of which part of the body the cell comes from.
The DNA in a human cell is unique, the product of sexual reproduction that combines half of the mother’s DNA and half of the father’s DNA. Every cell in an individual’s body is the result of cellular division, which copies the DNA in the newly fertilized cell into every other nucleic cell. As a result, DNA in a cellular nucleus is identical throughout a human body but variable between any two humans, making it a natural alternative to artificial human identifiers, such as names or tax-file numbers. The notable exception is identical twins, which develop from a single fertilized cell and hence have identical nuclear DNA...............
