Given below are two statements; one is labelled as assertion (A) and other is labelled as Reason (R).

Assertion (A): In gel-electrophoresis, DNA fragments are separated.

Reason (R): DNA is negatively charged so it moves towards the cathode under the influence of electric field.

In the light of the above sentences, choose the correct answer from the options given below:

A is true but R is false.

The correct answer is Option (3) -A is true but R is false.

During gel electrophoresis, DNA fragments separate based on their size and charge. The gel, typically made of agarose, acts as a molecular sieve that slows down the movement of DNA fragments as they migrate through the gel under the influence of an electric field.

When an electric field is applied, the negatively charged DNA fragments move towards the positively charged anode. Smaller DNA fragments can move through the gel more easily and thus migrate faster towards the anode compared to larger fragments. As a result, DNA fragments separate into distinct bands according to their size, with smaller fragments traveling farther from the origin (where the DNA was initially loaded onto the gel) and larger fragments staying closer to the origin.

By using this principle, researchers can analyze and purify DNA fragments of interest, allowing them to study specific genes or genetic sequences, identify mutations, or perform various other molecular biology techniques.