If there were alternate structures that preserved the information, evolution would continue unimpeded. This claim can be further examined in yet another intuition pump. Imagine that on another planet, “odd-numbered” generations used the DNA rungs A, C, G, and T, and “even-numbered” generations used a different double helix, call it XNA, with rungs made of P, Q, R, and S (some other molecules). We can suppose that the offspring’s XNA molecules were made from DNA templates from their parents by a mechanism rather like messenger RNA, but “translating” between the two different biochemical languages.
Source:
Philosopher Daniel Dennett’s Book Intuition Pumps
