Genetic defects, the result of changes in the genetic material of the chromosomes themselves, can be passed on generation by generation, or may skip generations.
基因缺陷是指父親或母親染色體的「遺傳物質」發生變異；它可能代代相傳，也可隔代遺傳。像小頭症、肌肉萎縮症、軟骨發育不全… … 等均是。