Why can gel electrophoresis separate DNA fragments?

O

A. DNA fragments are positively charged.

O

O

B. DNA fragments are negatively charged.

C. DNA fragments are all the same size.

D. DNA fragments are magnetic,

The correct option is B) DNA fragments are negatively charged.

Explanation:

The backbone of the DNA is made up of sugar and phosphates. The phosphates present in the backbone of the DNA are the main reason for the DNA to be negatively charged. The negative charge of the DNA allows different DNA fragments to separate by gel electrophoresis depending on their charge/mass ratio. The smaller DNA fragments will move faster towards the positive end of the gel as compared to the larger fragments and hence they will separate.