Gene drive can be explained as a phenomenon whereby a particular gene via genetic engineering methods biases inheritance in its favour (more than the Mendelian 50:50 inheritance chance) resulting in the gene becoming more prevalent in the population over successive generations. The speed of this process is inversely correlated to the generation time of the organism, eg: it is faster in mosquitoes with a generation time of 2-4 weeks than in whales with generation time of 50 years or more.
This idea is mostly being explored as a potentially durable and cost effective strategy for controlling the transmission of deadly vector-borne diseases that effect millions of people worldwide such as malaria, dengue, Zika virus, or to eliminate herbicide or pesticide resistance. Eg: The Cas9 mediated gene drive led by Gantz et. al. in the mosquito population by introgression of parasite-resistance genes, thereby modifying the ability of the vector to transmit the pathogen.
Though the dangers of this technology cannot be overlooked. One of the ideas was a suggestion to use CRISPR gene editing technology to avert extinction of endangered wildlife by spreading a fertility reducing gene in the other animals competing against them for resources. This with time turned from an innovative idea to a perilious one, as demonstrated in a CRISPR-Cas9 gene drive targetted at genes that control the differentiation of the two sexes of the Anopheles gambiae mosquitoes. Leaving the males unaffected it decreased the fertility of the female mosquitoes. The gene rapidly spread reaching 100% prevalence within 7-11 generation to the point of total population collapse despite various Cas9-resistant genes arising in each generation.
With just a few of these engineered organisms our ecosystem could be altered, irrevocably.
References: 1) Gantz, V. M., Jasinskiene, N., Tatarenkova, O., Fazekas, A., Macias, V. M., Bier, E., & James, A. A. (2015). Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi. Proceedings of the National Academy of Sciences, 112(49), E6736. https://doi.org/10.1073/pnas.1521077112
2) Kyrou, K., Hammond, A., Galizi, R. et al. A CRISPR–Cas9 gene drive targeting doublesex causes complete population suppression in caged Anopheles gambiae mosquitoes. Nat Biotechnol 36, 1062–1066 (2018). https://doi.org/10.1038/nbt.4245
3) Emerson, C., James, S., Littler, K., & Randazzo, F. (Fil). (2017). Principles for gene drive research. Science, 358(6367), 1135. https://doi.org/10.1126/science.aap9026
4) Alphey, L. S., Crisanti, A., Randazzo, F. (Fil), & Akbari, O. S. (2020). Opinion: Standardizing the definition of gene drive. Proceedings of the National Academy of Sciences, 117(49), 30864. https://doi.org/10.1073/pnas.2020417117
