Question

In gel electrophoresis of DNA, toward which electrode do the DNA fragments migrate?

• A. Positive electrode (Anode)
• B. Negative electrode (Cathode)
• C. Both electrodes equally
• D. They do not migrate

Hint:

DNA has a {negative phosphate backbone}. Hence in electrophoresis:
{DNA → moves toward the positive electrode (Anode)}.

Answer 1

The Correct Option is A

Topic: Molecular Biology (Gel Electrophoresis)
Gel electrophoresis is a method used to separate DNA fragments based on their length by pulling them through a gel matrix using an electric current.
Steps:
Understanding the Question: To determine the direction of migration, we must know the electrical charge of DNA and basic laws of electrostatics.
Key Formulas and Approach: DNA contains a phosphate backbone ($PO_4^{3-}$). Opposite charges attract.
Detailed Solution:
DNA is a negatively charged molecule because of the phosphate groups in its sugar-phosphate backbone.
When placed in an electric field, a negative molecule will move away from the negative pole (cathode) and toward the positive pole (anode).
As the fragments move toward the anode, the gel matrix acts as a sieve, allowing smaller fragments to move faster than larger ones.