does ethidium bromide untwist DNA
Ethidium bromide is an intercalcating dye, which means it inserts itself between the bases that are stacked in the center of the DNA helix. One ethidium bromide molecule binds to one base. As each dye molecule binds to the bases the helix is unwound to accommodate the strain from the dye.Closed circular DNA is constrained and cannot withstand as much twisting strain as can linear DNA, so circular DNA cannot bind as much dye as can linear DNA.ne ethidium bromide molecule binds to one base. As each dye molecule binds to the bases the helix is unwound to accommodate the strain from the dye. Closed circular DNA is constrained and cannot withstand as much twisting strain as can linear DNA, so circular DNA cannot bind as much dye as can linear DNA.