Lose the megabyte and bit analogy and use the proper terms for a start. Its megabases for a start and nucleic acids instead of bits.
DNA has nothing to do with computers so please don't confuse the two.
Everything has to do with information/computing. The whole universe can be broken down to 1/0s (and 1 and 0 at the same time if you are in to quantum physics). The universe is literally just information. There is an interesting physics theory that it might not even be real, but a projection of information stored at the edge of the universe or the surface of black holes.
http://en.wikipedia.org/wiki/Holographic_principle