Which one of the following statements is incorrect about gel electrophoresis?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → In gel electrophoresis, the larger the fragment, the farther it moves.
(1) The DNA fragments separate according to size through the gel. — A correct statement. The agarose gel works like a sieve, so the fragments separate by size.
(2) Separated DNA fragments in electrophoresis can be visualized only after staining the DNA. — A correct statement. Pure DNA cannot be seen in visible light. It is stained with ethidium bromide and then seen as orange bands under UV light.
(3) Most commonly used matrix in electrophoresis is agarose. — A correct statement. Agarose is a natural polymer taken from seaweeds.
(4) In gel electrophoresis, the larger the fragment, the farther it moves. — The incorrect statement. It is the other way round. DNA is negatively charged, so it moves towards the anode. Small fragments pass through the pores of the gel easily and move farther. Large fragments are held back and stay closer to the well.
NCERT Extract:
Restriction Enzymes – “… Nowadays the most commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves.”