Gene drives meet germline biology

I’ve written previously about gene drive technology, which allows gene editing of entire species. This works by engineering alleles that are inherited at greater than the expected Mendelian frequency of 50%. One example is a CRISPR gene introduced into mosquitoes that copies itself to all offspring, while making only the female offspring sterile. This results in an increase in the proportion of males, shortly followed by a population crash.I wrote “Gene drives: why the wait?” nearly four years ago, and since then we’re still waiting for gene drive deployment. Mainly this is due to political roadblocks, but there is also the concern that the gene drives will lose efficacy and generate resistance in the target species.Mechanisms of resistanceResistance to gene drives is an undesired side effect of their mechanism of spreading. Sometimes instead of copying the drive allele over into the wild-type allele, the drive breaks the wild-type allele in such a way that it generates a resistant…