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

Concept: Gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric field across a gel matrix. DNA molecules carry an overall negative charge due to the presence of phosphate groups in their backbone.
Step 1:Charge on DNA molecules.
The backbone of DNA contains phosphate groups, each carrying a negative charge. As a result, DNA fragments behave as negatively charged molecules in an electric field.
Step 2:Movement in an electric field.
When an electric current is applied, negatively charged molecules migrate toward the positively charged electrode (anode).
Step 3:Separation in the gel matrix.
As DNA fragments move through the agarose gel, smaller fragments migrate faster and travel farther than larger fragments, allowing separation based on size. Therefore, DNA fragments migrate toward the positive electrode (anode) during gel electrophoresis.