How is DNA Profiling carried out?

Step 1: Get a sample of DNA.
This can be obtained from almost all parts of the human body like blood, skin, hair, etc.
Step 2: Lyse the cell
The cell is broken down to release DNA.
DNA is taken from it using a solution of salt or chloroform and phenol.
DNA can be copied through this process as well as being split down for examination. It is being amplified using the polymerase chain reaction or PCR.
Step 3: Cut the DNA
The DNA is cut into fragments using restriction enzymes. DNA is split when heated, which means that the double helix is splitted into two halves. Once the DNA has cooled it will form a new set of building blocks, which will repair the two halves. Each cell contains around six feet of DNA strand when viewed under an electron microscope.
The restriction enzymes will cut the DNA at a specific base sequence. These sections that are cut by the enzymes are known as restriction fragments. As a result, thousands of restriction fragments of all different sizes are yielded. This is because the base sequence could be either close together or far apart.
Step 4: Separation of fragments based on size
The fragments are classified according to their respective sizes using gel electrophoresis. The gel used here is commonly agarose gel which provides a matrix for with pores for the molecules to travel through and be sorted by size.
The DNA fragments are injected into wells and an electric current is applied along the gel.
As the overall charge of DNA is negative, it is attracted to the positive terminal of the gel. Like chromatography, the shorter DNA moves faster than the longer ones. As DNA is colourless, staining the gel with substances like methylene blue is important so that the DNA fragments can be seen. Also, a radioactive material is added which combines with the DNA fragments to produce a fluorescent image and this enables a photographic copy of the DNA fragments to be taken.
Step 5: Analyse the pattern of the DNA fragment distribution
The analysation of the DNA sample is done as final step. This allows the forensic scientists to conclude and solve the mysteries in crimes or diagnose medical problems.

Real Life DNA Analysis

Source(s):

• http://www.exploreforensics.co.uk/taking-dna-samples.html
• http://en.wikipedia.org/wiki/DNA_profiling
• http://www.biotechnologyonline.gov.au/popups/int_dnaprofiling.html