NEW YORK (Dispatches)-Researchers are rewriting the yeast genome from scratch as part of a controversial project aiming to create custom-made chunks of DNA codes.
New York University researcher Jef Boeke is heading a team of scientists from 11 labs across four continents who are working to "rewrite" the yeast genome, following a detailed plan they published in March.
One goal of the project is to create codes that can be inserted into cells to alter their function or even improve drug development. For example, mammalian cells or microbes could be created that are better at pumping out medications or new vaccines.  
Although yeast has a larger and more complex genome than the microbes investigated so far, researchers understand the yeast genome well and they know it will exchange man-made DNA for its own. So far, Boeke and colleagues have built about one-third of the genome, which they hope will be completed by the end of the year.
The research may reveal basic, hidden rules that govern the structure and functioning of genomes. But it also opens the door to life with new and useful characteristics, like microbes or mammal cells that are better than current ones at pumping out medications in pharmaceutical factories, or new vaccines. The right modifications might make yeast efficiently produce new biofuels, Boeke says.
Some scientists look further into the future and see things like trees that purify water supplies and plants that detect explosives at airports and shopping malls.
Also, scientists are working on redesigning human DNA. That's not to make genetically altered people, they stress. Instead, the synthetic DNA would be put into cells, to make them better at pumping out pharmaceutical proteins, for example, or perhaps to engineer stem cells as a safer source of lab-grown tissue and organs for transplanting into patients.
Some have found the idea of remaking human DNA disconcerting, and scientists plan to get guidance from ethicists and the public before they try it.