How DNA Testing Works

DNA is found within each cell of our bodies. It is the genetic "plan" that makes us who we are. Only identical twins share this blueprint; everyone else is genetically unique.

The sampling process collects cells from the inside of your mouth from which DNA is extracted.

The test analyses certain parts of the DNA molecule, known as STR (Short Tandem Repeat), which are chosen for their variability between different people. We generally use between 15 and 19 of these STR DNA markers.

Since everyone inherits half of their DNA from their mother and half from their father, related individuals are more likely to share the same version of these genetic markers than people who are unrelated. The probability of two people being related can be calculated using the frequency of their DNA pattern in the general population.

For example in the case of paternity testing, since a child has inherited one half of her DNA from her mother and one half from her father, if the man tested shares one gene copy with the child at each DNA marker then there is a greater than 99.99% chance that he is the biological father.

If he does not share a gene copy at two or more DNA markers then he is not the biological father of the child.

In rare cases, a biological father may not share a gene copy with his child at one DNA marker as a result of mutation. Please see our 'Find Out More' page for more information.