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DNA

DNA (Deoxyribonucleic Acid)

DNA contains coding instructions for a range of cellular components in all living organisms. Bacteria, insects, plants, fish, birds and humans all contain DNA.

In humans, most DNA is packaged into 46 separate molecules called chromosomes. These chromosomes each contain thousands of genes, with each gene specifying how to make a particular protein.

DNA spells out our genetic information using a defined sequence of chemical building blocks. Specific regions of non-coding DNA can vary between individuals in the general population. It is these variable DNA sequences that are targeted in forensic DNA profiling.

DNA is inherited from each of our parents, and can be used for paternity testing.

Identical twins will have the same forensic DNA profile (but different fingerprints).

Forensic Science and DNA

Criminal investigators have hailed DNA analysis as the most important advance in fighting crime since fingerprinting. DNA testing in criminal investigations has grown rapidly over the years and is used for a wide range of offences.

Forensic DNA scientists across Australia routinely test the same nine variable DNA regions, plus a test for gender.

A typical male DNA profile looks like this: 

14,15    17,18    23,24    X,Y    13,13    30,30    15,19    11,11    11,11    10,11

Experts look for matches between DNA extracted from blood or other biological material left at the scene of a crime, and DNA taken from a suspect.

If the DNA profiles do not match, then the suspect can be excluded as the source of the DNA detected at the crime scene.

In Tasmania, forensic DNA profiling is regulated by the Forensic Procedures Act 2000. DNA profiles from convicted criminals are held on a DNA database, and are routinely compared to DNA from crime scene samples.