Describe the method of separation& isolation of DNA fragments . OR Explain the technique of gel electrophoresis used to separate DNA fragments in biotechnology .

The molecule of  DNA can be cut by the enzyme restriction endonucleases. These fragments of DNA can be separated by a technique known as gel electrophoresis.

DNA fragments are negatively charged molecules which can be separated by forcing them to move towards the anode under an electric field through a medium / matrix called agarose – a natural polymer extracted from sea weeds.

 The DNA fragments separate according to their size through sieving effect provided by the agarose gel such that the smaller fragment moves through a longer distance.

DNA  fragments can be visualised as bright orange coloured bands only after staining the DNA with ethidium bromide followed by exposure to UV radiation.

The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece by elution.