Here the unique thing was that there's a restriction site inside that is present in normal DNA and not present in sickle DNA.

刚才例子中,特性就是在正常的基因中,有酶切位点,而在患者的基因中却没有

耶鲁公开课 - 生物医学工程探索课程节选

In this case, this particular restriction enzyme cuts symmetrically like this, but not at the same point.

在我们这种情况下,这个限制性内切酶总是这样对称地切割,但两条链切割的位点不一样

耶鲁公开课 - 生物医学工程探索课程节选