There are two reasons for the relatively poor stability of the genetic structure of influenza and for its tendency to mutate. First, unlike our genetic code, which is stored on long double strands of DNA, the genetic code of influenza is stored on long single strands of RNA. The double-stranded DNA is just plain stronger than the single-stranded RNA and so less likely to break and recombine in weird and unexpected ways. The second reason is that the double-stranded DNA genetic code contains duplicate information, which allows copies to be checked for accuracy during reproduction. Most viral RNA, on the other hand—including that of influenza—lacks this extra information, so the inevitable random errors cannot be detected or corrected.