But it seems that in many cases, healthy genes are damaged by outside agents ​ — radiation and chemicals being among the prime suspects.
لكن على ما يظهر تتضرر في حالات كثيرة مورِّثات طبيعية بفعل عوامل خارجية ،‏ اهمها الاشعة والمواد الكيميائية .‏