The Death and Life of the Great Lakes by Dan Egan:
The biological bombshell that arrived at an Auburn University laboratory in 2009 came in the tiniest of packages—a cardboard box about the ize of a paperback book. Inside it were several plastic tubes that contained flecks so small that they were invisible. Lab workers tipped these tubes into a solution that was as innocuous looking as a glass of water. It was anything but. In it floated a designer “poison” potent enough to eradicate an entire fish population.
The concoction, which held a specially modified fish gene built in a high-security laboratory on the Australian island of Tasmania, was placed into Petri dishes thick with E.coli bacteria and then dosed with a chemical that allowed the bacteria to absorb the genetic material. As the fast-reproducing E.coli numbers then exploded, copies of the gene replicated right along with it, with two new genes emerging each time a bacteria cell split. In a matter of hours the Auburn biologists had untold millions of E.coli, each carrying a strand of the manmade genetic code. And each of those strands held the power to take a species’ collective sex drive and throw it in reverse, to turn sexual reproduction from a life-sparking act into a life-snuffing one.
It does so by adding a twist in the DNA so a fish implanted with the gene can produce only male offspring. The concept, called the “daughterless gene,” is devilishly clever: a developing carp turns female only after an enzyme transforms the male hormone androgen into the femal hormone estrogen. This gene blocks production of that enzyme, so the embryonic fish cannot make the early-life transformation from male to female. The idea is that if you plant enough of these daughterless fish into a lake or river for a sustained period, it’s just a matter of time until it runs out of females to carry on a population. The fish breed themselves into oblivion.