Epigenetics—currently one of molecular biology's hottest topics —is a process by which genes are activated or deactivated by the presence or absence of chemical structures called methyl and acetyl groups.

表现遗传学——目前分子生物学最热的话题之一——是这样一个过程，基因的激活或是失效取决于被称为甲基和乙酰基的化学结构的存在或是消失。

It replaced one of salicylic acid's hydroxyl group — that's an oxygen and hydrogen bonded to a carbon — with an acetyl group, which is two carbons, one double-bonded to an oxygen and the other bonded to three hydrogens.

它用乙酰基取代了水杨酸的一个羟基——氧和氢与碳结合——乙酰基是两个碳，一个与氧双键结合，另一个与三个氢结合。