对所有pcr产物电泳没有条带的样本进行重复提取pcr过程中增加了阴性对照使用超纯水代替了DNA。所有阴性对照在电泳中均为呈现条带。将这段话翻译成英文。

All samples without bands in PCR products were re-extracted in duplicate, and negative controls were added during the PCR process, in which ultrapure water was used instead of DNA. All negative controls showed bands in the electrophoresis.