This process of using a biological event like resistance to Ampicillin in order to pick out the cell population that you're interested in is called selection.

这个利用生物特性,如对氨苄青霉素的抗性,来挑出你所感兴趣的细胞的过程叫筛选

耶鲁公开课 - 生物医学工程探索课程节选

In another example, you can use a "when" question in order to ask about the timing of a specific event.

在下面这个例子中，你可以用When 问句来询问一个具体活动的时间。

When 课堂 - SpeakingMax英语口语达人