琼脂糖凝胶电泳EB是加在胶中,为什么只有在有DNA的地方有荧光呢?

Ethidium bromide is an intercalating agent,when exposed to ultraviolet light,it will fluoresce with an orange colour。When DNA is moving in the gel,it binds EB during its moving。Therefore,DNA band has more fluoresce than the background。
1。to your question,"是不是在跑的过程中DNA可以富集胶内的EB",the answer is yes。
2。EB is thought to act as a mutagen because it intercalates double stranded DNA,thereby deforming the molecule。This can affect DNA biological processes,like DNA replication and transcription。So,EB会致癌。
3。You do not have to add more EB when you re-melt EB-containing gel。
4。When you heat the EB-containing gel,very trace EB could come to the air together with water vapor。You can compare to heating the gel with and without EB,you can tell。