Arrange the given steps involved in gel electrophoresis used for separation of DNA fragments?

(A) Exposure to UV light

(B) Staining with ethidium bromide

(C) Moving of DNA fragments towards anode

(D) Elution

The correct option is (B), (A), (D), (C).

Here is the detailed step-by-step explanation of the sequence of events involved in this gel electrophoresis and recovery workflow:

1. Staining with ethidium bromide (B):
DNA molecules are colorless and cannot be directly seen in an agarose gel under normal light. Therefore, the gel containing the DNA is stained with a fluorescent dye, most commonly ethidium bromide (EtBr), which intercalates between the nitrogenous bases of the DNA double helix.

2. Exposure to UV light (A):
After staining, the gel is exposed to ultraviolet (UV) radiation. The intercalated ethidium bromide fluoresces under UV light, revealing the DNA fragments as distinct, bright orange-colored bands against the dark background of the gel.

3. Elution (D):
Once the target DNA bands are located and visualized, the specific gel segments containing the desired DNA fragments are physically cut out of the agarose gel slab. The DNA is then extracted and purified from these gel slices, a process known as elution.

4. Moving of DNA fragments towards anode (C):
In specialized recovery techniques like electroelution, the eluted DNA within the recovery chamber is subjected to an electric field. Because DNA carries a net negative charge due to its phosphate backbone, the DNA fragments migrate through the buffer solution towards the positive electrode, which is the anode, to be collected and concentrated.