The experimental procedure that begins with a cloned segment of DNA, or a protein sequence, and uses this knowledge to introduce programmed mutations (through directed mutagenesis) back into the genome in order to investigate gene and protein function.

• 在已知DNA克隆片段或蛋白质序列上引导程序性的变异（通过直接诱变）并返回到基因组，来研究基因和蛋白质功能的实验方法。