9.5 A gene drive that reduces fitness
You should have found that the analytical model works well for gene drives that have no effect on fitness. However, I said above that we were going to look at an example of evolutionary engineering did affect fitness—by design—in a specific way.
Kyros Kyrou, Andrew M. Hammond, and colleagues designed their gene drive to render female homozygotes completely infertile. The drive does so by inserting itself into a gene, called doublesex, that plays a crucial role in sex-specific aspects of development. Data on the reproductive output of the mosquitoes show that it works as intended:
![A gene drive targetting the doublesex gene makes female homozygotes infertile. Modified from Kyrous et al. 2018.](images/gene-drive-kyrou-data-fitness.png)
The data show no significant differences in the number of larvae produced by ++, male D+, female D+, and male DD mosquitoes. Female DD mosquitoes, however, produce no larvae at all.
The scientists have checked off two of the three items in our evolutionary engineering challenge: