Electrophoresis

Electrophoresis is used as a method of separating DNA according to size, using a porous gel as a filter. Gels are used to prevent convection currents. Polyacrylamide gels are used and separates proteins depending on charge, size and shape. The speed of the migration of the macromolecules is also influenced by the gel's pore size. There are two separate portions presence across the gel, stacking gel and resolving gel. The stacking gel consists low percentage of polyacrylamide where bigger molecule tends to move slower. While the resolving gel contains higher percentage of polyacrylamide, which the smaller molecule can move faster and further in distance.  By applying an electric current, the molecules of DNA are made to move through the gel towards the positive electrode (anode), with the smaller or more compact strands travelling the fastest. This produces distinct bands of DNA, which can be identified by comparing with a known DNA sample 'ladder' run simultaeously. Any molecule with a net charge, such as proteins, can also be seperated using this technique.

The mobility of charges molecules are influenced by:

• Net Charge of molecule. Negitive charged molecules move towards the positive end of the electrode (anode) while positive charged molecule move towards the negitive end of electrode (cathode). 
• Size of molecule
• Shape
• Electrical field strength applied