You could imagine strategies where you have multiple resistance genes on a plasmid, resistance to Ampicillin, to Penicillin, to Erythromycin for example, and you design strategies for separating out which cells are carrying the plasmid that you're interested in.

若质粒上有多种抗性基因,你就有很多筛选方法,例如对氨苄青霉素,青霉素,红霉素的抗性,而且你可以设计方法分离出,含有你感兴趣质粒的细胞

耶鲁公开课 - 生物医学工程探索课程节选

Plus,if you're looking for insulin, if you're looking for the gene for insulin you're going to cells that are making it already, they have abundant messenger RNA so it's much easier to separate out and identify the gene that you're interested in.

再者,如果你在找胰岛素,如果你在找胰岛素基因,你要到,正在制造胰岛素的细胞里找,里面有丰富的mRNA,所以更容易分离,并识别出你感兴趣的基因

耶鲁公开课 - 生物医学工程探索课程节选