The Read/Write Metaphor Is a Flawed Way to Talk About DNA

In 2014, chemist Floyd Romesberg, of the Scripps Research Institute, synthesized a new pair of artificial nucleotides and got a cell to accept them as part of its genetic code. In metaphorical terms, he extended the alphabet of life. To review, the DNA molecule is built from four nucleotides, or “letters”: adenine (A), thymine (T), guanine (G) and cytosine (C). Each letter is one half of a pair—A always goes with T, and G with C—and each pair forms a single rung of the molecule’s twisted ladder. Romesberg’s team, after years of work, synthesized a third pair—X and Y—and inserted it successfully into the code of a bacterium, which then reproduced, maintaining its synthetic code. Life on Earth depends on …

Gene Editing Is Trickier Than Expectedbut Fixes Are in Sight

Of all the big, world-remaking bets on the genome-editing tool known as Crispr, perhaps none is more tantalizing than its potential to edit some of humanity’s worst diseases right out of the history books. Just this week, Crispr Therapeutics announced it had begun treating patients with an inherited blood disorder called beta thalassemia, in the Western drug industry’s first test of the technology for genetic disease. But despite the progress, there remain a host of unknowns standing in the way of Crispr-based medicines going mainstream, chief among them safety. That’s because the classic, most widely used version of Crispr works by slicing open a strand of DNA in a specific spot in the genome and letting the cell stitch it …