DNA stands for Deoxyribonucleic Acid. It is a molecule not just found in the cells of people but, animals and plants.
DNA holds the genetic code that makes us all very unique. Our height, sex, hair, eye colour and other personal features contribute to the variations in the code. 50% of our DNA was inherited from each parent. Siblings are more likely to have similar DNA than unrelated people.
Imagine a tangled knot of very thin strands; that is how DNA exists in the cells of our body but it is invisible. If we straightened it out, the DNA from each cell would stretch to two metres long. It is difficult to imagine that we have more than six feet of it inside a cell and it is actually invisible to the human eye!
If we took the DNA from all the cells in our body it would stretch to the sun and back not once or twice but a whopping 500 times. We have more than 45,000,000,000 miles of DNA!
DNA Crime Prevention and Detection.
Given that it is highly likely for a sample of DNA to be found at the scene of crime, it can be used in a number of ways. It can be compared with a sample that has been taken from a suspect. A positive match can be used as evidence.
DNA can be taken from a suspect and checked against the National DNA Database. DNA taken from other crime scenes may be linked to that person. DNA can positively identify offenders through DNA taken from close relatives.
DNA isn’t just about catching criminals; it is also used to eliminate suspects and identification of bodies.
DNA can be used to mark property and aid recovery from the thieves.
How is DNA used?
DNA doesn’t need to be surgically removed, simply by using a buccal swab (buccal meaning inner-cheek) and gently rubbing the inside of the cheek, DNA from the mouth cells are collected and can be forensically analysed
Like fingerprints, not every single difference between people’s DNA is required. Techniques are deployed to look at specific areas of DNA that are conclusively known to vary widely between people. This technique is called ‘DNA Profiling?it analyses and measures the recorded differences to link the DNA with the suspect and crime scene or weapon.
The National DNA Database is used by every police force in the UK to compare DNA taken from scenes of crime. At present there are over two million samples of DNA taken from individuals that are stored on the DNA Database.
It might be that DNA is only present in tiny amounts. These can be greatly amplified using a technique called Polymerisation Chain Reaction (PCR). This can produce a positive result from just one nanogram (one thousand millionth of a gram) of DNA.
Profiling is conducted in the forensic science laboratory and takes between 16 and depending on the DNA sample.