DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as :

The correct option/answer is: Bright orange bands

Step-by-Step Explanation:

1. Ethidium Bromide Staining: Ethidium bromide (EtBr) is a widely used fluorescent dye in molecular biology laboratories. It intercalates, or inserts itself, between the stacked base pairs of double-stranded DNA molecules in an agarose gel.

2. UV Radiation Exposure: Ethidium bromide itself absorbs ultraviolet (UV) light, specifically in the range of 300 to 360 nm. Once it is intercalated within the DNA and excited by UV light, it fluoresces strongly.

3. Visualization: The fluorescence emitted by the DNA-bound ethidium bromide is in the visible spectrum. When the stained gel is exposed to a UV transilluminator, the DNA strands appear as distinct bright orange bands against a darker background.