Smith says he faced a puzzling problem with the lamprey genome, though. Some DNA sequence he had produced from lamprey sperm cells simply wasn't lining up with the lamprey genome assembled by Sanger. Some bits aligned partially, and then veered off into unmatched DNA. Other bits were completely without a match. "That turned out to be a red herring in a sense," he says. The sequence wasn't lining up because up to about half a billion basepairs of DNA found in the reproductive cells of lampreys is deleted from all other adult cells.
Much of Smith's work has since been trying to figure out both why and how the lamprey seems to make about 20% of its genome disappear during the development of all but its gametes.