Question

1.Describe the respective function of the agarose gel, electrophoresis buffer and power supply, in the set-up of electrophoresis. (1)

2.State three precautions in the process of setting up the digestion of DNA. (0.75)

3.To visualize the DNA bands on gel, one can use Midori-green or a DNA probe.

a. Explain the underlying principle of both methods, respectively. (2.5)

b. Suggest one advantage and disadvantage for each method, respectively. (1)

Answer 1

1.

Gel electrophoresis is a technique which is used to separate a mixture of substances on the basis of their size and charge.

Agarose gel acts as a sieve for the separation of nucleic acid fragments. It is used for the separation of RNA and DNA molecules. As the concentration of gel increases, the size of the pore decreases and the resolution of the gel increases. This gel helps in the separation of even smaller fragments of nucleic acids. Molecules move according to their size on the gel. Smaller the fragment is, faster it moves on the gel and the farthest it appears on the gel picture.

Electrophoresis buffer is used in electrophoresis for maintaining a constant pH. If pH is disrupted, then samples will not move in an appropriate manner and there will be no separation of molecules.

Power supply is used for the generation of electricity. The nucleic acid fragments are also separated on the basis of charge. The samples are loaded at the positive electrode and move towards the negative electrode. So this movement occur because of the conduction of electricity which is provided by the power supply.

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