What is the final step after gel electrophoresis to obtain purified DNA fragments?

Cutting out DNA bands from the gel

The correct answer is Option (3)- Cutting out DNA bands from the gel

Explanation:

After gel electrophoresis, the DNA fragments are separated based on their size in the agarose gel. Once the gel electrophoresis is completed, the researcher can visualize the DNA fragments in the gel using ethidium bromide staining and UV light exposure (option a and b). The next step is to carefully cut out the specific DNA bands from the gel. These excised DNA bands represent the desired DNA fragments that need to be purified from the gel.

After the DNA bands are excised, the DNA can be extracted from the gel pieces using methods like gel elution or electroelution, which involve using an electric field or diffusion to remove the DNA from the gel matrix.

The purified DNA fragments can then be used in downstream applications like gene cloning, DNA sequencing, PCR amplification, or other genetic manipulations. Mixing with cloning vectors (option d) is a subsequent step where the purified DNA fragments are inserted into the cloning vectors to create recombinant DNA for further studies, but it occurs after the gel extraction process.