These issues can be a deal-breaker when biologists want to make hundreds or thousands of changes to an organism's genome, says Chang Liu, a synthetic biologist at the University of California, Irvine. … “Now, I can make a series of changes in one segment and then another and combine them together. That's a big deal,” Liu says. The new tools will bolster industrial biotechnology by making it easier to vary the levels of proteins that microbes make, Liu and others say.