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.

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:

Design and build our own gene,

Put it into the genome of a living organism, where it will alter the fitness—in a precise way—of the individuals who carry it, and

Accurately predict how our gene’s frequency will change across many generations in a population.