What is gel electrophoresis?

Gel electrophoresis

• Electrophoresis is used for the separation and purification of DNA fragments by the application of electricity.

• A gel is used in electrophoresis that is polyacrylamide or agarose .

• Poly acrylamide is used to separate smaller fragments of DNA whereas agarose gel is used in separation of large fragments of DNA.

• Agarose gel is powder that has been extracted from seaweeds. Agarose when mixed with the water and boiled  it assumed the gel-like appearance.

• Agarose gel is mixed with Water and salt to become a good conductor of electricity.

• Agarose gel forms small pores. These pore act as a sieve that allows the larger molecule to move more slowly than smaller molecule.

• A box of electrophoresis has both positive and negative electrodes, A shelf to hold the gel , a comb  and power supply.

• During electrophoresis, The DNA is digested by the restriction  enzyme. As a result , DNA fragments are formed with unequal length.

Read more about the Restriction enzyme

• These  fragments are mixed with Ethidium di bromide or methylene blue. 

• These both dye Ethidium di bromide or methylene blue are sucrose containing dye and known as loading dye.

• This current is allowed between the Negative electrodes at the top of loading end and Positive electrodes at the bottom of loading end.

• DNA molecules are negatively charged so opposite electric charges attract each other. Consequently , small DNA fragments move faster than larger fragments.

• All DNA fragments migrate into gel and form the bands. After that, gel is removed from the chamber and separated bands of DNA are extracted. This is called elution.

• The DNA bands are stained with Ethidium dibromide or methylene blue and seen under Ultraviolet light.

Read more about the Polymerase chain reaction

• The DNA fragments appear as orange or blue colored bands.