There are common differences, like the differences between blue eyes and brown eyes, or even between people likely to have Crohn’s disease and those who are unlikely to have it. Then there are differences that result simply from a “broken” gene, which is not a variant but simply a mistake.
这种差异既有共性的方面，例如蓝色眼睛和棕色眼睛的差异，也有克罗恩氏症易感人群和非易感人群之间的差异。此外还有单纯因基因“遭受破坏”而导致的差异，它不是一种变异，而仅仅是一种错误。其中的绝大多数都没有危害，真正有危害的变异存活时间太短，也因此不为人知。