Which of the following is TRUE for gel electrophoresis ?

(A) It is used to separate DNA fragments.
(B) Separation of DNA occurs on the basis of the fragment size.
(C) Separation of DNA fragments occurs on the basis of charge.
(D) Separated DNA fragments can be visualised without staining.

Choose the correct answer from the options given below:

(A) and (B) Only

The correct answer is Option (4) → (A) and (B) Only

When DNA is cut into fragments by restriction endonucleases, these fragments can be separated using a technique called gel electrophoresis.  Because DNA fragments are negatively charged molecules, they can be moved towards the anode (positively charged electrode) when subjected to an electric field within a gel-like matrix. This electric field causes the DNA fragments to migrate through the gel. The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves.

To visualize the separated DNA fragments, a specific compound called ethidium bromide is used for staining. After the gel electrophoresis process, the gel is treated with ethidium bromide, and then it is exposed to UV radiation. This step is crucial because pure DNA fragments are not visible to the naked eye under normal visible light and without staining.