Genes are located on what and each gene controls a specific what

Genes are segments of DNA located on chromosomes and they contain the code used to synthesize a protein.

So to answer your question, I'd say: Genes are located on chromosomes and each gene controls a specific trait.  

What some science videos to you

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