A generation ago, DNA was scary or, at best, exotic stuff. Now, thanks to CSI and its progeny, DNA seems familiar to most people. It's the mysterious substance that frees the innocent and determines the father of Anna Nicole's Smith baby. Everybody "knows" what DNA is. It has a warm, fuzzy image in the public mind.
For audiences who know a little more about it, DNA also has glamour. Understanding how it works doesn't cancel the mystery of life encoded, replicated, and wildly varying. Like a spiral staircase, the very shape of the DNA molecule suggests hidden wonders. As the photo above suggests, even Hollywood wants in on the glamour. The double helix image is bound to break out of nerd culture into more general design use. One example: Grant McCracken blogged from Poland about this woman's double-helix tattoo, complete with base pairs.