the selective advantage of a gene is determined by all the other genes in the genome, as well as to lesser or greater extent all the other genes in everyone else's genomes too. the only thing is, that you can't change a gene (sequence) while it's in use to adapt to the current situation, you have to wait a generation and hope that there are "better" variants around. ensembles of genes acting in networks probably take on adaptive properties, but this adaptiveness seems to be occurring on the level of network dynamics, and not at the level of gene sequences (in one generation).
tags - how do you track them? - letters are like base pairs, but words are like proteins, you're more concerned with their functions than their spelling.