Question

In agarose gel electrophoresis, DNA molecules are separated on the basis of their ______.

Options

• size only

• charge only

• charge to size ratio

• all of these

Answer 1

In agarose gel electrophoresis, DNA molecules are separated on the basis of their size, charge and charge to size ratio.

Explanation:

In agarose gel electrophoresis, DNA molecules are separated based on more than one factor:

• DNA molecules carry a negative charge due to their phosphate backbone, so they move in an electric field towards the positive electrode (anode).
• The gel matrix acts like a sieve and separates DNA fragments primarily according to their size smaller fragments move faster and farther than larger ones.
• Therefore, the migration depends on the charge to size ratio, as DNA molecules have a uniform negative charge per unit length, making charge proportional to size.