Holy crap! This is so clever!!
Component #1– Anopheles gambiae, the kind of mosquito that is notorious for spreading malaria.
It might seem as if there is no way these two components could come together in any meaningful way.
But when you are an evil scientist, anything is possible!!
It turns out that there is a DNA sequence on the X-chromosome of the mosquito that the homing endonuclease recognizes. Unlike restriction enzymes, where the DNA match has to be (pretty much) perfect, there is some wiggle-room with homing endonucleases (the mosquito DNA isnt a *perfect* match, but its good enough).
So, if this enzyme was present in mosquito cells, it would slice the X-chromosome in two.
That is not overly helpful.
If you start slicing up the X-chromosome, the mosquitoes would be non-viable. Male and female. The point isnt to kill mosquitoes, here.
So, the researchers genetically modified the enzyme so it would only be expressed during spermatogenesis, and it would have a really short half-life (it would break-down and become non-functional relatively quickly).
Translation: Male mosquitoes that had this gene engineered into their genomes would only make sperm with Y chromosomes. Very few or no X chromosomes. Meaning mostly all of their offspring would be male. The enzyme would be degraded by the time fertilization occurred, so it shouldnt accidentally slice up the necessary X-chromosome from mom-mosquito.
Lots and lots of viable baby male mosquitoes.
Male mosquitoes do not feed off of humans, meaning they dont transmit malaria or other pathogens.
And, having males dominate the progeny means that the mosquito population would go down (whereas having mostly females would cause the population to boom). The idea to mess around with mosquito population sex ratios to control population size has been around since 1966. This is just the first time in history we have had the technology to carry it out.
Of course there are concerns about ‘resistance’ (the mosquito populations evolving around the genetic modification), which this paper addresses. And they didnt address the impact a smaller mosquito population would have on the populations of other organisms (somebody has to eat them, right?). But considering the number of people who get sick and die from malaria every year (not including all the other mosquito-born pathogens!), this might be a great first-step in a positive direction.