“WHEN IS A gene editor not a gene editor?” may sound like a scientific riddle with a groan-worthy(令人呻吟的，老套的) punch line. But it is a question whose answer instead deserves many an appreciative intake of breath(赞叹的吸气声). That is because scientists keen to achieve more precise control over an organism’s genetics are experimenting with a surprising approach that leaves the genome itself unharmed.
“什么时候基因编辑器不是基因编辑器？”听起来像是一个科学谜语，答案可能让人哭笑不得。但这个问题实际上值得人们深深赞叹。这是因为渴望更精确控制生物基因组的科学家们正在尝试一种令人惊讶的方法，这种方法不损害基因组本身。
The principle behind gene editing sounds simple. Molecules of DNA contain strings of chemicals called bases, sometimes referred to as the letters of the genetic alphabet. Alter this sequence of letters and genes can be turned on or off at will. It is a trendy(时髦的，流行的) idea already being applied in agriculture. But so far just one medical intervention has been approved: switching on a gene normally active only in infants to treat sickle-cell anaemia(镰状细胞贫血) and beta-thalassaemia, two blood diseases, in adults.
基因编辑的原理听起来很简单。DNA分子包含称为碱基的化学链，有时被称为基因字母表的字母。改变这个字母序列，基因就可以随意打开或关闭。这是一个时髦的想法，已经应用于农业。但到目前为止，只有一种医疗干预措施获得批准：开启一种通常只在婴儿体内活跃的基因，以治疗成人镰状细胞贫血和β-地中海贫血这两种血液疾病。
The lack of medical deployment is, in part, because gene editing can go wrong. It requires cutting the DNA molecule and an off-target(脱靶的) cut might, for example, disable an anticancer gene with possibly serious consequences. That provides an opening for an alternative. Epigenetic editing, as this alternative is called, employs similar biotechnology to gene editing but makes no cuts in the DNA. Instead it tinker(修补，小修小改)s with the epigenome, a set of chemical markers attached to the genome that regulate genes’ activities. The tinkering is less intrusive(侵入性的) than gene editing, and allows a gene’s output to be modulated, rather than simply switched on or off.
医学应用缺乏的部分原因是基因编辑可能出错。它需要切割DNA分子，而脱靶切割可能会使抗癌基因失活，可能造成严重后果。这为替代方案提供了机会。表观基因组编辑，正如这种替代方案所称，采用与基因编辑类似的生物技术，但不切割DNA。相反，它修补表观基因组，这是一组附着在基因组上调节基因活性的化学标记。这种修补比基因编辑侵入性更小，并允许调节基因的输出，而不是简单地打开或关闭。
Intellectual inheritance
知识遗产