Question

Why fragments of different sizes cannot be separated by standard electrophoresis?

Answer 1

Electrophoresis:

1. Electrophoresis is the technique used to segregate DNA, RNA, and protein molecules based on their size and electric charge.
2. In this technique, the charged molecules are suspended in a gel and when an electric current is applied, the molecules migrate through the gel.
3. The DNA strands have an overall negative charge and in an electrophoretic gradient, they all move towards the positive pole.
4. The migration speed depends on the charge-to-mass ratio and shape of the strand.
5. As all DNA fragments have a similar shape and move towards the positive pole, fragments of different sizes cannot be separated by this method.
6. Size markers are co-electrophoresed along with DNA samples to determine the size of fragments.