I think what he's getting at is that you can look at the genome of E. coli, which was sequenced in the nineties, and is one of the most common model systems use

I think what he's getting at is that you can look at the genome of E. coli, which was sequenced in the nineties, and is one of the most common model systems used in research, but we don't know what the functions of a lot of those genes are. Last time I heard anything about this we had no idea what twenty percent of its genes did. That number may be off by ten to fifteen percent either way, since I haven't read anything on the topic in years, and it's going to depend on the parameters you set for how sure you are about a gene's function. Keep in mind that this doesn't mean we're completely clueless about how the cell works, just that there's still a lot of work to do.