DNA Profiling
What is dna?
DNA is short for Deoxyribonucleic acid. DNA is a molecule that carries most of the genetic instructions for the developing and functioning all living things. In short DNA is what makes us grow and function. DNA is personal to all of us and is and can be used to identify us, biologically. DNA is material that determines our eye color, hair color, stature, bone density and many other human and animal traits. DNA is a long, but narrow string-like object (see the picture on the right for a computer simulated image).
What is dna profiling?DNA profiling is a technique used to identify individuals by characteristics of their DNA. DNA profiling uses things like fingerprints, blood, saliva or semen to determine the likelihood that genetic material (blood, saliva, skin, hair etc.) came from a particular person or family group. It does not contain additional information on genetic relationships between people, their cultural origin or whether they are susceptibility to specific diseases - this is called 'Whole Genome Sequencing' and was developed in 1985.
|
COMMon sources of dna evidence
The following list shows some common sources of DNA evidence:
How do the police use DNA?
The police use DNA to try and identify things like fingerprints, blood, saliva or semen found at the scene of a crime and link them to who they came from. Unless you have an identical twin then your DNA is specific to you, so if its found at the scene of a crime it ties you to that person or location - it doesn't mean you did the crime but it does mean you've been to the scene, or come in to contact with the victim at some point.
POLICE DATABASE - Over the last 100 years police have built up a huge database of fingerprints and the DNA records of people who have been arrested. Using this as a starting point they can often link any good samples of DNA found at a crime scene to the records of already known criminals in the database.
INCLUSION OF A SUSPECT- If the DNA found at the scene matches a person then they will be included in the investigation as a suspect.
EXCLUSION OF A SUSPECT- If the DNA found at the scene DOES NOT match a person then that person may be excluded from the investigation as a suspect on the grounds of DNA evidence.
DNA was first used in July 1901 in a burglary case. This was the first criminal conviction using fingerprints as evidence to prove that the suspect was the man who broke in to a house. This fingerprint evidence led to his conviction and prison sentence in 1902.
POLICE DATABASE - Over the last 100 years police have built up a huge database of fingerprints and the DNA records of people who have been arrested. Using this as a starting point they can often link any good samples of DNA found at a crime scene to the records of already known criminals in the database.
INCLUSION OF A SUSPECT- If the DNA found at the scene matches a person then they will be included in the investigation as a suspect.
EXCLUSION OF A SUSPECT- If the DNA found at the scene DOES NOT match a person then that person may be excluded from the investigation as a suspect on the grounds of DNA evidence.
DNA was first used in July 1901 in a burglary case. This was the first criminal conviction using fingerprints as evidence to prove that the suspect was the man who broke in to a house. This fingerprint evidence led to his conviction and prison sentence in 1902.