ABSTRACT
In suppression drives, a genetic modification that induces a decrease in population size is spread. To accomplish this, an altered allele is spread that is harmful to the organism (e.g., causes death or sterility) when two copies are available (homozygous recessive). Suppression drives rely on the introduction of strongly or mildly deleterious mutations. They are intended to reduce or eliminate a population. The gene drives that are currently in development or that have already been applied in suppressing populations include meiotic drives (autosomal- or Y-linked X-shredder), maternal effect dominant embryonic arrest (Medea) systems, and CRISPR-Cas, to mention only a few. CRISPR-Cas9 gene drives fall into the category of homing endonuclease gene drives. The fact that using gene drives can lead to the spread of fitness-reducing traits (including lethality and sterility) makes it an attractive process to consider exploiting when developing methods to control disease vectors such as malaria-transmitting mosquitoes, ecosystem management, eradicating invasive species, and other agricultural pests. Suppression gene drives have been proposed to eliminate A. gambiae species to eliminate malaria in Africa. Gene drives are also being considered as a way of controlling other invasive species, including wasps in New Zealand. Scientists have demonstrated a proof-of-concept population conversion drive that could form the basis of various population suppression strategies in a species of fruit fly whose larvae feed on soft fruits such as cherries.
