ZFNs (Zinc Finger Nucleases) are engineered proteins that induce double strand breaks at specific sites in an organism's DNA. Scientists have successfully used this technology to generate transgenic Rats with heritable gene mutations without the need of using nuclear transfer or embryonic stem cells. Their study was published in July 24, 2009 issue of Science. This technology could be used to make disease state modes for research studies. It is early in development...so time will tell if it will become a useful and broad technology. For more see this link.