Question

Which of the following is true for agarose gel during electrophoresis?

• A. The larger the fragment size, the farther it moves
• B. The smaller the fragment size, the farther it moves
• C. Positively charged fragments move to farther end
• D. Negatively charged fragments move to farther end

Answer 1

The correct option is B The smaller the fragment size, the farther it moves

Gel electrophoresis is a technique for separation of DNA strands of different sizes using electric current.

Agarose gel acts as a sieve to selectively allow movement of DNA based on size. The smaller fragments will move faster compared to larger fragments.

DNA molecules are negatively charged due to the phosphate backbone.

Positive and negative electrodes are present on the two sides of the gel.

DNA sample is added to the wells near the negative electrode. When the current is passed through the gel, the DNA starts moving towards the positive electrode. Here, the smaller fragments moves quickly and reaches the farther end while the larger fragments trail behind. The DNA containing ethidium bromide is observed under UV lights.