How does the process of gel electrophoresis separate dna fragments?

DNA is negatively charged due to its phosphate groups. Gel electrophoresis has one side that is positive and other that is negative. Once dna fragments are placed inside. The bigger fragments will move towards the positive side since positive is attracted to negative.

For the separation of DNA fragments we use gel electrophoresis.

Explanation:

Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the positive electrode anode under an electric field through a medium or matrix. The most common matrix is agarose. The DNA fragments separate according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves. The separated DNA fragments can be visualized only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiations. You can see the bright orange colored bands of DNA in a ethidium bromide stained gel exposed to UV light.