Question

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

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

Answer 1

The Correct Option is C

The question asks about the appearance of DNA strands on a gel that has been stained with ethidium bromide, when viewed under UV radiation. Let's break this down step-by-step:

1. Understanding Ethidium Bromide: Ethidium bromide (EtBr) is a commonly used fluorescent dye in molecular biology. It intercalates between the base pairs of DNA.
2. UV Radiation Activation: When exposed to ultraviolet (UV) light, ethidium bromide emits fluorescence. This property is utilized in gel electrophoresis to visualize DNA.
3. Emitted Color Observation: When excited with UV light, ethidium bromide emits a bright orange fluorescence. This is due to its specific fluorescent emission spectrum.

Therefore, when you look at a DNA gel stained with ethidium bromide under UV light, the DNA bands appear as bright orange bands. This distinctive orange color helps researchers to see the location and size of the DNA fragments after electrophoresis.

Justification of Options:

• Bright blue bands: This would typically be seen with other dyes or staining methods, but not with ethidium bromide under UV light.
• Yellow bands: This is not the color emitted by ethidium bromide under UV light.
• Bright orange bands: Correct, as explained above. This is the characteristic fluorescence observed with ethidium bromide.
• Dark red bands: This is not observed in this context and does not refer to the emission of ethidium bromide under UV light.

In conclusion, upon viewing DNA gel stained with ethidium bromide under UV light, the DNA strands appear as bright orange bands, making option "Bright orange bands" the correct answer.