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#ethidium bromide

5 public questions tagged with this topic.

Mutation and Mutagenesis

Ethidium bromide is a

Ethidium bromide is cationic phenanthridine dye with flat polycyclic ring system ideally dimensioned to intercalate between nitrogenous bases, binding with high affinity and enhancing fluorescence twentyfold enabling visualization of DNA under UV. Intercalation lengthens and rigidifies duplex, inhibits topoisomerases, and promotes polymerase slippage leading principally to frameshift events rather than point substitutions. Due to potent mutagenic and potential carcinogenic activity, laboratory handling requires protective measures and decontamination with activated charcoal or hypophosphorous

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 9: Ethidium Bromide as Intercalating Agent

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Electrophoresis

EtBr binds to DNA at:

Ethidium bromide exhibits two binding modes to DNA. Primary high-affinity interaction involves intercalation between adjacent base pairs, causing helix unwinding and lengthening. Secondary electrostatic interaction occurs in minor groove where phenanthridinium ring contacts phosphate backbone. Crystallographic and spectroscopic studies indicate preferential residence in minor groove environment with partial intercalation, enhancing fluorescence quantum yield. Major groove binding is less favored due to steric hindrance. Sugar backbone and phosphate alone do not account for fluorescence enhance

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophoresis

Which stain allows DNA visualization under UV light?

DNA visualization requires a fluorophore excitable by UV transillumination. Ethidium bromide intercalates between base pairs and shows strong fluorescence enhancement upon binding, emitting orange light under UV. This allows detection of nanogram quantities of DNA within gel bands. Bromophenol blue and methyl blue are tracking dyes visible in white light, not fluorescent. Crystal violet stains proteins or bacterial cell walls and does not intercalate DNA. Therefore, ethidium bromide remains the prototypical UV-activated DNA stain, though safer alternatives like SYBR Green are now favored.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophoresis

What is the role of ethidium bromide in electrophoresis?

Ethidium bromide is a cationic phenanthridinium dye that intercalates between stacked base pairs of double-stranded DNA, with approximately one dye per 2.5 base pairs. Intercalation extends the helix and, upon UV excitation at 300 to 360 nm, emits orange fluorescence at 590 nm, enabling visualization of DNA bands within agarose or polyacrylamide gels. It does not participate in gel polymerization, does not denature DNA, nor catalyze reactions. While mutagenic and now often replaced by safer dyes, its mechanism remains classic DNA staining by intercalation.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Restriction Digestion & Mapping

EtBr staining visualizes:

Ethidium bromide is a planar intercalating dye that inserts between stacked base pairs of double-stranded DNA regardless of topology, sequence, or labeling status. Upon UV illumination at 300 nm, intercalated dye fluoresces bright orange, revealing all DNA present in gel lane. It does not differentiate labeled versus unlabeled molecules, linear versus circular conformations, as intercalation depends only on double helix presence. Specialized methods like autoradiography detect only radioactive termini, while EtBr provides universal visualization of total DNA population for size estimation afte

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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