I asked for questions and Robert obliged:
What’s “gene driving”? I saw it in context of malaria irradication techniques.
A gene drive is a technique used in order to force a certain gene variant (allele) to become prevalent in a target species — for example, a gene rendering males of the species half as fertile as normal, perhaps. A lot of people are aware of how reproduction usually works and the fact there’s usually a 50/50 chance for offspring to inherit a gene from one parent, but a gene drive gives a chance pretty close to 100%. How’s that work?
Well, first the gene for the gene drive must be introduced to the target species. It will consist of a pair of “molecular scissors” which can cut DNA (cas9 of CRISPR fame is a good choice), something to target it so it will cut the right DNA, and finally whatever we want to introduce in place of the original gene. Once that change is established, we rely on what we know about cells’ own DNA repair mechanisms. Normally, when a DNA strand is damaged, it is repaired by copying the other strand of the DNA. The unaltered, “wildtype” strand is cut at the right point by the scissors, and then the wildtype strand is fixed with reference to the strand with the gene drive. The gene drive perpetuates itself by targeting the wildtype version of the gene and replacing it with itself, so it only needs to be successfully inserted once in order to propagate through a population.
That’s what makes a gene drive so useful — once started, it’s bound to continue because it just replaces the competing DNA with copies of itself. One strand is enough to ensure that all daughter cells have two copies. In the case of irradicating a particular species, you can use this to break the gene, replace it with something nonfunctional, or replace it with something that harms the carrier.
There are some concerns and caveats about gene drives and the ethics (and ultimate usefulness) thereof, but it’s a pretty attractive tool in the arsenal when it comes to controlling invasive species, pests, etc.