Arrange the following steps of gel electrophoresis in correct sequenc…

The correct answer is Option (1) → (B), (D), (A), (C)

(B) Movement of DNA fragments towards anode under an electric field through agarose — first. DNA is negatively charged, so it moves to the anode.

(D) Separation of DNA fragments according to their size — second. The agarose acts as a sieve, so smaller fragments move farther.

(A) Staining the DNA with ethidium bromide — third. DNA cannot be seen until it is stained.

(C) Exposure to UV radiation — last. The stained DNA shows as bright orange bands in UV light.

NCERT Extract:
Restriction Enzymes – “… Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. 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.”
Restriction Enzymes – “The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation (you cannot see pure DNA fragments in the visible light and without staining). You can see bright orange coloured bands of DNA in a ethidium bromide stained gel exposed to UV light (Figure 9.3). The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution.”