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Right-handed and left-handed helices

 Is your model a right-handed helix or a left-handed helix? If you hold it pointing away from you and it twists clockwise moving away, it is right-handed, otherwise it is left-handed. These models are mirror images and can not be converted one into the other by rotation. The helix of normal DNA is right-handed. Left-handed helices have been produced experimentally and may be present in living cells.