It is a fact widely ignored by people who design covers for science books and journals, but let me say it loud and clear, the normal version of the DNA double helix is RIGHT-HANDED, i.e. it is like an ordinary screw in that if you look down the axis and follow the ridge clockwise, the movement will lead away from you (see this example from the Ashmolean Museum's collection of glassware).
If, however, you take a picture of a DNA double helix and mirror it, you end up with something blatantly WRONG like the examples below:
PS in order to inject some scientific method into my rant, I've just done a Google image search for "DNA" and checked the first 30 double helix images shown. Giving those where the chirality isn't easy to see the benefit of the doubt, I have spotted three images with left-handed helices, so the error rate seems to be around 10%, even on websites that get high PageRank.