Gene drive refers to the process by which a genetic element biases its own inheritance, and the genetic element itself.
Many natural gene drives have been identified that operate through a range of mechanisms. The CRISPR nucleases have accelerated the development of synthetic gene drives by making it easier to genetically engineer non-model species and a CRISPR nuclease is frequently used as a core component of the synthetic inheritance biasing mechanism.
Gene drives can through higher-than-normal rates of inheritance spread a genetic change through a population. This can occur even if the modification has a fitness disadvantage for those carrying it.
Homing endonuclease gene drives (HEGs) are likely the furthest developed form of synthetic gene drives. In diploids, one chromosome is contributed by the father and one by the mother. HEGs operate by copying themselves from one homologous chromosome to the other (switching the cell from being heterozygotes to homozygous from the HEG). Thus, while a mutation spread through Mendelian inheritance can propagate to only 50% of descendants with each generation, a modification spread through gene drives (or "super-Mendelian" inheritance) is passed on to virtually all descendants within a single generation.[1]
Two applications of gene drives to the control of malaria have been proposed. One is to modify the relevant mosquito species to make it incapable of carrying the malaria parasite. The other is to significantly reduce the population of those mosquito species.[2] Once the gene drives are released, the relevant mutation could be propagated through the entire population of interest in a period of just a few years. In 2016, a group of researchers at Imperial College and other universities genetically engineered the Anopheles gambiae mosquito—the primary mosquito species that spreads the malaria parasite—rendering it capable of passing the genetic modification to over 99% of offspring.[1]
Target Malaria is one organization currently working on these applications.
Gene drives have also been suggested for reducing wild-animal suffering. For example, transhumanist philosopher David Pearce proposes CRISPR-based gene drives for promoting low-pain alleles in sexually reproducing wild animals.[2] The leader of the MIT Media Lab’s Sculpting Evolution group Kevin M. Esvelt also has written favorably about engineered gene drives for reducing wild-animal suffering.[3]