> We've had astronauts in orbit
> for a few months with minimal resupply, and they have few health
> problems other than some musculo-skeletal degeneration,
NASA is beginning to work on gene expression studies. I'm fairly confident that within a few years we will be able to pick out the "gravity activated" regulatory factors and be working on ways to manipulate them via drugs or GenEng.
> Rebuilding a viable population wouldn't take more than a few tons
> of humans--a dozen young, healthy, diverse fertile women and a
> dewar full of sperm--but any small lack of foresight or setback
> that prevented them from bearing healthy fertile children would
> doom the colony, and we'd need about 16 years before we'd know.
Lee my good fellow, why on Earth would you want to continue propagating the alphabet soup that constitutes our genome? Are you a closet luddite sent to spy on us?
Seriously, if we can take the human genome apart in less than a generation, I don't see why we can't engineer a better one in the same time (given the march of the underlying technologies). [The point to this is highly questionable however, given the possibility of nanotech and uploads, but we'll assume we want some fallback position in case a luddite virus wipes out the uploads.]