Scientists have taken an important step toward a gene therapy that could one day turn off the extra genetic material that causes Down syndrome (DS). Down syndrome is a genetic condition caused by an extra chromosome 21 (and consequently hundreds of triplicate genes) that leads to developmental and neurological issues. According to the Washington-based National Down Syndrome Society, approximately 1 in every 640 babies in the United States is born with DS. That makes it the most common chromosomal condition.

Traditional gene therapy targets one or two genes, but in this approach, scientists at Beth Israel Deaconess Medical Center and Harvard Medical School found a way to silence much of the extra chromosome’s activity in the cell at once.

Details of their research are published in a paper in the journal Proceedings of the National Academy of Sciences.