I have a couple of questions about these drugs: 1. Does anyone know how acyclovir resistance occurs? First AID says mutated viral thymidine kinase, but apparently there are qbank questions that want you to know that resistance is due to lack of thymidine kinase enzyme (not alteration). Anyone know which? 2. For ganciclovir: is it doing two different things? It works as a chain terminator, but also directly inhibits CMV DNA polymerase? Or are these two mechanisms interconnected? Thanks!