The use of Crispr as a technology for genome editing has been around for a few years and burst into prominence in 2015, after the American Association for the Advancement of Science chose it as the breakthrough technology of the year. And as if genome editing wasn’t already a precision task, researchers from Massachusetts Institute of Technology (MIT) have added a light-based layer of control to the system.

According to a statement published on the MIT website Thursday, the method its researchers have developed allows Crispr to be used only when ultraviolet light is shone on the target cells, effectively making the light a switch.

Sangeeta Bhatia, a professor at MIT and senior author of a research paper that describes the new technique, said in the statement: “The advantage of adding switches of any kind is to give precise control over activation in space or time.” It could enable scientists to study the timing of cellular and genetic events that affect various bodily functions, from embryonic development to progression of diseases.

“Eventually, it could also offer a more targeted way to turn off cancer-causing genes in tumor cells,” the statement said.

Piyush Jain, the paper’s lead author, had “developed a way to use light to control a process called RNA interference, in which small strands of RNA are delivered to cells to temporarily block specific genes” before he came to MIT.

“While he was here, Crispr burst onto the scene and he got very excited about the prospect of using light to activate Crispr in the same way,” Bhatia explained.

This is not the first light-sensitive approach to Crispr. The Cas9 enzyme — it is the component that does the actual gene deletion in the method — has been previously altered to begin making a cut in the DNA strand only when exposed to certain wavelengths of light. The MIT team’s approach is different because it targets the RNA strand that accompanies and guides Cas9 to its target.

Bhatia said “it could be easier to deliver these modified RNA guide strands than to program the target cells to produce light-sensitive Cas9.”

Funded by the Ludwig Center for Molecular Oncology, the Marie D. and Pierre Casimir-Lambert Fund, a Koch Institute Support Grant from the National Cancer Institute, and the Marble Center for Cancer Nanomedicine, the research is described in the latest edition of the journal Angewandte Chemie.