electrophoresis

• • Gel electrophoresis separates DNA or protein fragments by size.
  • An electrical current is applied across the gel.
  • Fragments move to the positive electrode because they have a negative charge
  • Phosphate groups have a negative charge so all the DNA fragments move towards the anode.
  • They move at different speeds due to their size.
• The gel is made with wells to accommodate the DNA into the gel.
• The gel is submerged in electrolyte such as salt solution so that the circuit is complete and an electrical current can flow.
• A DC current is used because this travels in one direction and you only want the DNA fragments to travel up the gel.
• A buffer solution is used to maintain a constant pH and avoid DNA being denatured.
• the agarose gel is used because it allows a matrix through which DNA fragments can travel. It slows their travel down based on their size.
• the power is switched off before the end because if all the fragments reach the end of the gel then no pattern will emerge.
• The gel is washed in alkaline buffer afterwards to denature the DNA fragments which separates the strands and exposes the bases.