Formamide denature secondary structure of RNA, so no dsRNA should be present. Then how intercalation is possible
It seems counterintuitive, but have a look here:
https://www.aatbio.com/resources/faq-frequently-asked-questions/Does-ethidium-bromide-stain-RNA
https://pubmed.ncbi.nlm.nih.gov/22585558/
EtBr (ethidium bromide) is a fluorescent dye that binds to nucleic acids and imparts a fluorescent signal when exposed to ultraviolet light. In Denaturing RNA Gel electrophoresis, EtBr binds to single stranded RNA molecules that have been denatured by heat, and gives a fluorescent signal that can be detected and used to identify and quantify the molecules.
Ethidium bromide (EtBr) is a fluorescent dye that can intercalate into the DNA and RNA double helix. When EtBr intercalates into the nucleic acid double helix, it causes a shift in the energy of the dye molecules, leading to an increase in fluorescence intensity. This shift in energy occurs because the dye molecule becomes more constrained when it is intercalated into the DNA or RNA, and this leads to changes in the electronic properties of the dye.
When exposed to ultraviolet light, EtBr molecules that are intercalated into nucleic acids absorb the light energy and become excited to a higher energy state. The excited EtBr molecule then relaxes back to its ground state, and in the process, it releases the excess energy in the form of visible light, which can be detected using a fluorescence detector or a gel documentation system.
These video playlists might be helpful to you:
https://www.youtube.com/playlist?list=PLzBiAPKi8vOPbE7Db9mKwloe34E8rXXEU
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