Laser-like accurracy not so laser-like

Science reported on Nov 12: iRNA (intereference RNAs) were hailed as a great breakthrough, seeming to target problematic genes very specifically and shut them off. It seems, while still promising, a few problems cropped up. Although some scientists dispute the claim, one cancer biologist noted an increase in the interferon pathway which our immune system uses against viral attacks.

The main problem is that the small iRNAs "are hitting unintended genes, in general they're finding that a dozen genes may affected by a single s[mall]iRNA.... Most gene expression varies by less than twofold when the siRNA doesn't fully match--often not enough to have a substantial biological impact on how a cell, on an animal, actually functions." It is not DNA that's directly affected but the RNA (which our cells use to make protein for the variety of tools the cell uses).