Centromeric DNA

I was just listening to a couple of interviews (1,2) about ENCODE, which were interesting (link from Jan Skotheim's cool blog).  But aside from the arguments about ENCODE, there was some talk about comparisons to the human genome project, and how the human genome project had a nice end goal, but that goal was perhaps a bit more subtle than most realize.  Specifically, they didn't sequence all of the genome, because they skipped some of the repeats and the centromeric regions.  Then, in discussing ENCODE, they talk about how one could define the entire genome as being "functional" by ENCODE's definition because DNA polymerase interacts with every base.

Anyway, I thought it was somehow weird/fun to think about the fact that we don't know the sequence of the centromeric regions, but we know that DNA polymerase gets in there and replicates it.  I don't know why this seems strange to me, but I guess I like to think about these situations where something goes through some unexplored region and comes out the other end without really revealing much about its journey.  It reminds of how we have laid down these huge transatlantic cables connecting the US to Europe (in 1858!).  They basically just put down a big wire running the entire distance.  The deep of the ocean is still largely a mystery, but these cables run right through it, with our information none the wiser for their deep-sea voyage.  Somehow, I find this cool...