I've always wondered how the cell knows that with this gene, you get an arm (very general but it gets the point across). It seems to me like giving someone a dictionary, but not teaching them the language. So, how can cells "read" the DNA.
Also, I was wondering if it is possible for another form of life to exist, totally independent of DNA/RNA, or even cells?
Basically, Cell is the container of DNA, and RNA reads DNA. Then RNA produces proteins (arm, eye, hair, everything) with this information, and DNA is also informed through the process.
Instead of dictionary, I prefer computer analogy; you hit keyboard and you see some characters appear on the screen. But actually when you first hit the key "e" for instance, you are sending some ASCII code to a reader, then reader translates this to 0s and 1s, information is processed, then it's sent to some 0s and 1s reader/processor. When it arrived to your screen it's already translated into pixel language.
Yet, this is an analogy, not the exact thing about DNA. And there are plenty of areas that we still don't know exactly how the entire mechanism work. If we knew, we would have produced an artificial life by now. But I think we are going there...
So this information flow is actually coding, translating, interpreting and decoding process. Each component (either in cell level or transistor level) has a limited language and limited capacity for specific task. DNA can not make protein by itself; and RNA can not produce a knowledge for organ making.
For the "possibility" of life in other galaxies is wide open issue; same atoms, same universal rules; why not? But since this is nothing but a probability yet, we can only speculate: Life must depend upon some reliable information mechanism, DNA or some other coding system. Doesn't really matter.
