As I understand it, these things combine with the targeted mRNA then degrade, so that the RNA is not available for translation.

 

My question is what is to stop more RNA from taking its place? I don't know much about the subject, sorry...I learnt about it as part of an interdisciplinary module.

The regulation is determined by the equilibrium between the target RNA and the sRNA. So if there is an excess of the target RNA it would be indeed translated. This would be a situation when no silencing occurs.

During silencing either the sRNA concentration would be increased or the mRNA decreased based on other regulatory mechanisms to determine their final balance.

Thanks for answering. I didn't realize the concentration played a role.