Explanation:

If you want to do gene editing, you'll need to get your gene into your cell. Viruses are really good at doing exactly that, so a lot of modern gene editing technology revolves around putting genes into modified viruses, then infecting your cells with those modified viruses.

As it turns out, a lot of cells also have a lot of anti-viral mechanisms. One of them is called the RNAi system. Basically, if the cell detects foreign DNA, the cell automatically assumes that that DNA is from a virus and shuts down any and all production of whatever gene happened to be in that DNA.

This can have amusing consequences, because if you manage to trick the cell into thinking that its own genes are a virus, you can effectively block the cell from expressing its own genes. This effect was discovered when scientists tried putting a purple gene into a flower, which inadvertently caused the flower to think that its own purple gene was a virus. The end result is that the flower turned white.

This effect turns out to be incredibly useful for scientific research, because it allows scientists to suppress any gene without needing to go through the hassle of gene editing the cell