Question

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

• A. Yellow bands
• B. Bright orange bands
• C. Dark red bands
• D. Bright blue bands

Answer 1

The Correct Option is B

The question pertains to how DNA appears when stained with ethidium bromide and viewed under UV radiation. Ethidium bromide (EtBr) is a fluorescent dye that binds to DNA and is often used in laboratories for visualizing nucleic acids in gel electrophoresis.

Here's the step-by-step explanation and reasoning:

1. Understanding Ethidium Bromide: Ethidium Bromide is an intercalating agent used to stain DNA in gel electrophoresis. When it intercalates between DNA base pairs, the DNA-EtBr complex exhibits fluorescent properties.
2. Fluorescence Under UV Light: When the gel containing DNA stained with ethidium bromide is exposed to ultraviolet (UV) light, the compound becomes excited and emits light.
3. Emission of Light: Ethidium bromide emits a fluorescent light when exposed to UV radiation. This fluorescence is predominantly in the orange spectrum.
4. Appearance of DNA Bands: The DNA, bound to ethidium bromide, thus appears as bright orange bands under UV light due to this fluorescence.

Therefore, when viewed under UV radiation, DNA strands on a gel stained with ethidium bromide appear as bright orange bands. This is the basis for selecting the correct answer.

Correct Answer: Bright orange bands

The other options such as yellow, dark red, or bright blue do not accurately describe the emission spectrum of ethidium bromide-stained DNA under UV light.