Trojan chromosomes: Sex-change weaponry

Nature reports on the latest way we’re fighting invasive exotic species… by changing the girls into boys:

In 2004, alerted to Florida’s problems with invasive species, Juan Gutierrez, a bio-mathematician at Florida State University, constructed a mathematical model of a population in which males carry two different sex chromosomes (XY) and females are XX. In many species of fish, amphibians, and other animals, gender is determined not only by sex chromosomes, as it is in humans, but also by environmental conditions such as the presence of hormones, explains Gutierrez.

By exposing genetic males to female hormones, or vice versa, it is therefore possible to create a male that is genetically XX, or a female that is XY or even YY. Such individuals, with the genetics of one sex but the physical characteristics of the other, are referred to as carriers of ‘Trojan sex chromosomes’.

In Gutierrez’s model, repeated introduction of YY females resulted in an extremely male-dominated population, as all offspring produced from meetings between males (XY) and YY females are male, and many more males are born in subsequent generations. With fewer and fewer females around, the birth rate declined and finally ground to a halt, and the population was extinct within just a few decades.