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Biology Question 108 – NEET-UG 2023

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Upon exposure to UV radiation, DNA stained with ethidium bromide will show

In molecular biology, specific dyes are used to make DNA visible under certain conditions.

Step 1: Identify the Staining Agent and Purpose✦ Active

The question refers to DNA stained with ethidium bromide (EtBr) and exposed to UV radiation. Ethidium bromide is a fluorescent intercalating agent commonly used to visualize DNA in techniques like agarose gel electrophoresis.

Step 2: Recall Fluorescence Properties○ Expand

When ethidium bromide binds to DNA, its fluorescence quantum yield increases significantly. Upon excitation with UV light (typically 300-360 nm), the EtBr-DNA complex emits light.

Step 3: Determine the Emitted Color○ Expand

The characteristic color of the light emitted by ethidium bromide-stained DNA under UV radiation is bright orange. This allows for the visualization of DNA bands or fragments.

💡 Teacher's Secret Hint

Remember that different fluorescent dyes emit different colors. For EtBr, it's always orange.

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