WIKIMEDIA, MAGGIE BARTLETT, NHGRICreating genetically modified mice for experiments can take months or even years, and making mice with multiple mutations can be especially time-consuming. But a new system for genetically engineering model organisms could reduce that time to under 4 weeks, according to a paper published last week (May 2) in Cell.

“This new method is a game changer,” Rudolf Jaenisch, an author of the paper, said in a press release from the Whitehead Institute in Cambridge, Massachusetts, where he is a founding member. “We can now make a mouse with five mutations in just 3 to 4 weeks, whereas the conventional way would take 3 to 4 years.”

Jaenisch and colleagues’ method takes advantage of a set of proteins and RNAs that bacteria use to degrade DNA from viruses and foreign plasmids. Called the CRISPR/Cas system, it works by recognizing foreign DNA and causing double-strand breaks....