What is DNA?
We're all born with deoxyribonucleic acid (DNA) in our cells. This unique combination of markers is unique to everyone on Earth and can only be found more than once in identical twins. DNA takes exactly the same form in every cell of the body, which is why semen, saliva, blood, skin and other biological samples will give a forensic scientist a complete profile of the person to whom it belongs. On the technical side, there are four DNA bases or building blocks in DNA: Cytosine, Guanine, Thymine and Adenine, regularly referred to as C, G, T and A.
Overview of DNA's discovery
When news broke that scientists Jim Watson and Francis Crick had figured out where to look to get a complete picture of an individual's hereditary information, only the scientific community and astute, forward-thinking people fully understood the implications of this break-through in 1953. The DNA helix, with confusing explanations of how it worked, were added to high school science books and slowly, DNA became a recognizable term used in everyday conversation. Watson and Crick's revelation of the "secret of life" languished nearly 30 years in laboratories and institutions of higher learning before law enforcement officials began to use it. A third researcher, based in the United Kingdom, proved the final link to the marriage between DNA and the International law enforcement community.
We're all born with deoxyribonucleic acid (DNA) in our cells. This unique combination of markers is unique to everyone on Earth and can only be found more than once in identical twins. DNA takes exactly the same form in every cell of the body, which is why semen, saliva, blood, skin and other biological samples will give a forensic scientist a complete profile of the person to whom it belongs. On the technical side, there are four DNA bases or building blocks in DNA: Cytosine, Guanine, Thymine and Adenine, regularly referred to as C, G, T and A.
Overview of DNA's discovery
When news broke that scientists Jim Watson and Francis Crick had figured out where to look to get a complete picture of an individual's hereditary information, only the scientific community and astute, forward-thinking people fully understood the implications of this break-through in 1953. The DNA helix, with confusing explanations of how it worked, were added to high school science books and slowly, DNA became a recognizable term used in everyday conversation. Watson and Crick's revelation of the "secret of life" languished nearly 30 years in laboratories and institutions of higher learning before law enforcement officials began to use it. A third researcher, based in the United Kingdom, proved the final link to the marriage between DNA and the International law enforcement community.
DNA is further explored as a forensic tool
The Watson/Crook collaboration earned honors and recognition, but for those in the law enforcement community seeking to hasten their conviction rates, Alec Jeffreys, an English geneticist, is the man to whom they owe the biggest debt. In 1985, Jeffreys conceived the idea of DNA fingerprinting (also known as DNA typing and DNA profiling) when he noticed that DNA samples contained adjacent sequences of markers that repeated over and over again. Comparing specimens, he concluded that these patterns of repetition made them unique to every individual on earth. He began experimenting with the identification of individuals using what has come to be known as his VNTR system (variable number of tandem repeats). From the repeats, RFLPs (restriction fragment length polymorphisms) were identified and added a final step in the art of DNA forensics.
Jeffrey' methodology stands up to a landmark test
British immigration authorities learned about Jeffreys' work and asked for his help solving a double homicide. He took samples collected at the crime scene and proved that only one perpetrator could have murdered the two victims. On that day, history was made, and the British legal and law enforcement communities were forever changed. As you can imagine, the international law enforcement agencies are not without their grapevines. The United States--and particularly the FBI--adopted DNA testing as the ultimate crime solving tool, despite the high cost of conducting the test. Since 1985, DNA testing and profiling has solved crimes, served as legal bases for opening old cases, freed convicted felons, and become the litmus test for the legal community seeking to convict or clear suspects. While the price of DNA testing continues to carry a hefty price tag, hundreds of public forensic labs and a growing number of private facilities are currently performing DNA testing around the globe.
How DNA is used in today's forensics investigation
At the crime scene, forensic scientists collect samples of often-minute biological materials--including blood, bone, hair, body fluids and tissue. A DNA profile is run and a panel of markers is established to identify the contributor of the sample. The DNA profile is then compared to samples lifted from other crime scenes, those taken from suspects and databases of DNA fingerprints collected from other sources. If there is no match, a suspect is ruled out. If there is a match, this doesn't mean that a person is declared guilty, but the likelihood that he was present at the crime scene can't be refuted.
In some cases, when DNA isn't available for comparison, the forensics team may request a sample of a relative's DNA since all humans inherit half of their markers from each parent. Additionally, a comparative database known as CODIS is available to all participating law enforcement agencies. This central resource is so efficient, it could easily have matched up evidence left behind by serial killer Ted Bundy from crime scenes stretching from Florida to Washington State by performing a single laboratory test.
The Watson/Crook collaboration earned honors and recognition, but for those in the law enforcement community seeking to hasten their conviction rates, Alec Jeffreys, an English geneticist, is the man to whom they owe the biggest debt. In 1985, Jeffreys conceived the idea of DNA fingerprinting (also known as DNA typing and DNA profiling) when he noticed that DNA samples contained adjacent sequences of markers that repeated over and over again. Comparing specimens, he concluded that these patterns of repetition made them unique to every individual on earth. He began experimenting with the identification of individuals using what has come to be known as his VNTR system (variable number of tandem repeats). From the repeats, RFLPs (restriction fragment length polymorphisms) were identified and added a final step in the art of DNA forensics.
Jeffrey' methodology stands up to a landmark test
British immigration authorities learned about Jeffreys' work and asked for his help solving a double homicide. He took samples collected at the crime scene and proved that only one perpetrator could have murdered the two victims. On that day, history was made, and the British legal and law enforcement communities were forever changed. As you can imagine, the international law enforcement agencies are not without their grapevines. The United States--and particularly the FBI--adopted DNA testing as the ultimate crime solving tool, despite the high cost of conducting the test. Since 1985, DNA testing and profiling has solved crimes, served as legal bases for opening old cases, freed convicted felons, and become the litmus test for the legal community seeking to convict or clear suspects. While the price of DNA testing continues to carry a hefty price tag, hundreds of public forensic labs and a growing number of private facilities are currently performing DNA testing around the globe.
How DNA is used in today's forensics investigation
At the crime scene, forensic scientists collect samples of often-minute biological materials--including blood, bone, hair, body fluids and tissue. A DNA profile is run and a panel of markers is established to identify the contributor of the sample. The DNA profile is then compared to samples lifted from other crime scenes, those taken from suspects and databases of DNA fingerprints collected from other sources. If there is no match, a suspect is ruled out. If there is a match, this doesn't mean that a person is declared guilty, but the likelihood that he was present at the crime scene can't be refuted.
In some cases, when DNA isn't available for comparison, the forensics team may request a sample of a relative's DNA since all humans inherit half of their markers from each parent. Additionally, a comparative database known as CODIS is available to all participating law enforcement agencies. This central resource is so efficient, it could easily have matched up evidence left behind by serial killer Ted Bundy from crime scenes stretching from Florida to Washington State by performing a single laboratory test.
