And the reason is because in certain individuals, they can actually have genetic changes or mutations that are not passed down from the mother or from the father, but actually start brand new in them, mutations that are present in the egg or the sperm at the time of conception but have not been passed down generation through generation within the family.
原因就在于，对于某些个体而言， 他们实际上会发生基因变化， 或者说变异， 而这些并非继承自他们的母亲 或者父亲， 而是在他们自己体内才开始的产生， 也就是说卵子或精子 受育过程中 发生的突变， 并不是随着家族 代代相传而导致的。