What happens to dna as generations of a species continue to reproduce

Over time mutations occur. If the mutation is null (no effect) or beneficial, the organism will go on to reproduce and that mutation will carry into the next generation. Faulty mutations that cause harm will not likely be carried forward.
So, several generations later you have some level of change to the original sequence.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it