Figure 5. Methods of reversing, preventing, and controlling the spread and effects of gene drives.
(A) Reversal drives could correct or reverse genomic alterations made by an earlier drive with unexpected side effects. They might also be used to reverse conventionally engineered or evolved changes. Immunization drives could prevent other gene drives from affecting a specific population or provide a population with resistance to DNA viruses. Precision drives could exclusively spread through a subpopulation with a unique gene or sequence. (B) Together, these can quickly halt an unwanted drive and eventually restore the sequence to the original wild-type save for the residual Cas9 and guide RNAs. (C) Any population with limited gene flow can be given a unique sequence by releasing drives A and B in quick succession. So long as drive A does not escape into other populations before it is completely replaced by drive B, subsequent precision drives can target population B without risking spread into other populations.