DNA, or deoxyribonucleic acid, carries the genetic information of a cell. The arrangement of the four nucleotides that make up DNA is the code which dictates protein synthesis in all living things.Elmhurst College Virtual Chembook: Nucleotides The nucleotides are arranged lengthwise along the DNA strand, which is paired with a second strand in an arrangement known as a double helix. The structure of DNA was identified by James Watson and Francis Crick in 1953.NovelPrize.org: The Discovery of the Molecular Structure of DNA — The Double Helix They were awarded the Nobel Prize in 1962 for their work.NobelPrize.org: The Nobel Prize in Physiology or Medicine — 1962

A section of DNA that influences a particular characteristic in an organism is known as a gene.Kids Health: What Is A Gene? The strands of DNA and the genes they contain are the mechanism by which inheritable traits, such as hair and eye color, are passed from one generation to the next.

An individual's DNA sequence is unique. Unless a person has an identical twin, the arrangement of nucleotides is different for each person. Consequently, DNA can be used to match cells left at a crime scene with a specific person. Forensic DNA technology is still evolving, but is being used to help solve both current cases and unresolved cold cases.KariSable.com: DNA And Forensic Science Criminal Investigations DNA Evidence has also been used to prove that previously convicted individuals were actually innocent of the crime they were convicted for.MSNBC: DNA Tests Clear Georgia Inmate of Rape Charges (December 8, 2005)

With the ability to identify specific genetic traits from DNA analysis comes the potential to examine an individual's DNA for markers that indicate a susceptibility to certain inherited diseases. In 2007, 23andMe began a service allowing people to check their own DNA history and susceptibility to illness and disease in exchange for $999.redOrbit: Start-Up Enables Users to Examine Their Own DNA (November 20, 2007)