Question

why is ethidium bromide added at this step?
○ ethidium bromide is needed to see the dna bands in the gel under uv illumination.
○ it helps with the separation of the bands according to size.
○ it conducts the electrical current through the gel.

Explanation:

Ethidium bromide is a fluorescent dye that intercalates into DNA. Under UV light, it emits a visible orange glow, allowing DNA bands separated by gel electrophoresis to be visualized. It does not aid in band separation (this is done by gel pore size and electric field) or conduct electricity (buffer solution handles that).

Answer:

Ethidium bromide is needed to see the DNA bands in the gel under UV illumination.