DNA Forensics/Testing:

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The application of DNA technology and the knowledge of DNA genetics to the practice of forensic medicine and to the power of legal medicine (MedicineNet). It is therefore a powerful tool for identification and has many practical applications in our everyday life.

Common Uses Include (BBC Science):

 Parental testing - to establish if someone is the biological parent of a child
 Forensic testing - to help identify suspects or victims in a criminal investigation
 Gene therapy - to test parents or foetuses for genetic conditions or birth defects
 Genetic genealogy - to find out more about someone's ancestry


What is the DNA Test looking for?

According to science reports about 99.9% of the DNA from two people will be identical hence only 0.1% of the DNA code sequences that varies from individuals to individuals are what makes us different.

These sequences are called genetic markers, and are the part of the code that forensic scientists use when doing a DNA test (BBC Science). Identical twins are the only people who have identical genetic markers while closely related people also have genetic markers that are similar.

The key to DNA testing is knowing where to look in the billions of letters of genetic code to find the genetic markers that will identify the important similarities or differences between people.


How does DNA test work? 

DNA testing of all types basically looks for similarities in the genetic markers between two biological samples. This is because all cells in the body contain exactly the same DNA, samples can be taken from almost anywhere in the body, including skin, hair follicles, blood and other bodily fluids.

 For example a DNA comparison can be made from skin cells found underneath the fingernails of an attack victim, with the cells from a blood sample taken from a potential suspect.

 First of all, the DNA is isolated from the cells and millions of copies are made, using a method called 'polymerase chain reaction', or PCR. According to BBC Science, this PCR uses a naturally occurring enzyme to copy a specific stretch of DNA over and over again. Having lots of DNA makes the genetic code easier to analyse.

The DNA molecules are then split at particular locations to separate them into known 'chunks' and the code at those specific points is analysed to create a DNA fingerprint. The fingerprints from the two different samples are then compared to see if they match.

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