Effects of a mutation can be
1.harmful
2.
3. neutral.
4.all of the above

ALL OF THE ABOVE BECAUSE IT IS HARMFUL AND HELPFUL AND NEUTRAL SO YEAH ALL OF THE ABOVE

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