Even if it did do something, there's a finite amount of it and it needs to be introduced into the cell in some way to have any effect. When siRNA experiments ar

Even if it did do something, there's a finite amount of it and it needs to be introduced into the cell in some way to have any effect. When siRNA experiments are done in a lab setting with human cells grown in a petri dish, one technique to make this happen is to actually shock the cells with just enough electricity to not kill them off, but to allow them to be in a certain state to take up the siRNA internally. Then, the effect only lasts as long as there is siRNA to silence mRNA transcripts. In other words over time normal expression patterns return as the siRNA is depleted and new mRNA is transcribed.