Question

What must be done before placing the DNA in the electrophoretic chamber?
A. It must be grounded with pestle and mortar
B. It must be cut with restriction endonucleases
C. It must be treated with RNAse
D. None of these

Answer 1

Electrophoresis is a technique by which charged biomolecules are separated based on their size and electrical charge. Molecules like DNA, proteins, RNA etc. can be separated through a gel when an electric current is passed through it. An electrophoretic chamber is filled with a gel, probably polyacrylamide or agarose gel and then wells are made into the gel which are filled with samples like DNA. Once the sample is loaded electrodes are attached to the electrophoretic chamber and then under the influence of current the charged particles move through the gel based on their size, charge and molecular weight.

Complete answer:
Option A: In this option it is said that DNA is grounded with pestle and mortar before loading into the gel. This does not go in hand with our discussion.
Thus, Option A is incorrect.
Option B: In this option the point mentioned is that DNA is cut by restriction enzymes before being loaded into the gel. This is what we have already discussed.
Thus, Option B is correct.
Option C: This option cannot be correct because it talks of treating DNA with RNAse which is of no use as RNAse digests RNA and has no effect on DNA.
So, Option C is also incorrect.
Option D: None of these. Since we have got the correct option already, this option is not possible.
Option D is incorrect

Hence, Option B is the correct answer.

Additional information:
DNA is a negatively charged molecule and therefore moves towards anode, the positively charged electrode. For this question to be answered one must know the steps of electrophoresis of DNA.
Steps of electrophoresis of DNA
Sample preparation
Preparation of gel and its casting
Adding sample
Running the gel
Visualization
The first step sample preparation is a crucial step and our answer lies in this step. Once the DNA is extracted from samples like blood etc. it is hydrolyzed into smaller fragments with the help of restriction endonuclease enzyme before being loaded into the electrophoretic chamber in the gel. These fragments of DNA are then separated by gel electrophoresis.

Note:
Electrophoresis can distinguish DNA fragments of different lengths. DNA is negatively charged, so when a current is applied to the gel, the DNA will migrate to the positively charged electrode. Shorter DNA strands migrate through the gel faster than longer DNA strands. As a result, the fragments are arranged in size. By using dyes, fluorescent labels, or radioactive labels, DNA can be seen on the gel after separation and displayed as bands on the gel.