第二部分大意：
碱基修正技术在去年被发现。这种技术结合了CRISPR-Cas9以及一种叫作胞苷脱氨（基）酶的酶，且该酶能够连接在DNA上。这种技术可以发现一个细胞中特定的G-C碱基对并转换成T-A碱基对。
在这周的自然杂志发表的论文中，另一项能够把A-T碱基对转换成G-C碱基对的碱基修正技术被发现。这个技术比先前的那一项要难得多，因为这个技术中用到的酶在自然界中不存在，于是发明这项技术的小组的成员创造了它。这项技术的成功率超过50%，比单用CRISPR-Cas9的4%成功率高出不少，且不会对DNA产生不必要的新增或者删减。
Base editing was invented last year. It combines CRISPR-Cas9 with a enzyme called cytidine deaminase, which can be bound to DNA and find specific G-C base pairs and convert them into T-A base pairs in a cell.
In one of the papers published by Nature this week, the extention of base editing technique which can convert A-T pairs into G-C ones was invented. It is harder than the one before because the enzyme it uses does not exist in nature, so the team who invented the technology set about creating it. It is proved to be effective more than half the time, which surpass the 4% when using CRISPR-Cas9 alone, and will not have unwanted insertion or deletion of DNA.
