Why does DNA twist?
If it did not twist, would you expect it to fit into the miniscule cell? As we all know, if we join all of the DNA molecules from a person's body end to end, we would get length three times the distance from the centre of the earth to the sun! Thus, DNA does not have a choice but to follow the super solenoid structure. This is also aided by the purine-pyrimidine linkages, to balance the weight of DNA components. Why pressing down on the cover slip does not remove surplus water.