Genomes of prokaryotes tend to have a higher proportion of coding DNA to non-coding DNA in their sequence than eukaryotes. This means that either eukaryotes accumulated lots of non-coding DNA, much of which is regulatory, in the course of evolution — or that prokaryotes lost this proportion of non-coding DNA.
In order for transcription of a particular gene to occur, it seems that there must be some search performed on the DNA sequence to find the gene to be transcribed.
This search seems to be independent of the sequence length — if it weren't, that could act as a selection pressure, inducing loss of DNA that doesn't do anything. Therefore, it seems that the method by which this search is done must be
O(1) — that is, it takes a constant amount of time to complete the search, regardless of the length of the sequence.
Such a method would be most welcome in computational sequence searches (in place of BLAST for example).
My question is, what, if anything, is currently known about the process of transcription that could explain this constant search time? Or, if I am completely wrong in my assumptions, what are more reasonable assumptions?