CRISPR gene drives bias inheritance so that a chosen genetic element is copied from one chromosome to its homolog during reproduction, increasing its frequency across generations. The concept builds on earlier work on homing endonucleases and more recent proposals to use CRISPR-Cas9 to achieve efficient copying. Austin Burt Imperial College London has described how a nuclease that cuts the wild type allele can be repaired using the drive-containing chromosome as a template, producing super-Mendelian transmission. Kevin Esvelt Massachusetts Institute of Technology has been a prominent voice on the laboratory design and ethical considerations for such systems.
Biological mechanism
At the molecular level the drive encodes Cas9 and a guide RNA targeted to the native sequence. When an organism heterozygous for the drive mates, the nuclease cuts the wild type allele in the zygote or germline. Homology directed repair then uses the drive allele as a template, converting a heterozygote into a homozygote and biasing inheritance above the normal 50 percent. Conversion efficiency, the rate at which this copying occurs, determines how rapidly the drive allele can increase in frequency. Competing processes such as inaccurate repair pathways can produce resistant alleles that no longer match the guide RNA, and fitness costs associated with the drive can slow or prevent spread. Laboratory studies led by Andrea Crisanti Imperial College London and others have demonstrated both efficient conversion and the emergence of resistance in mosquito systems, illustrating these tradeoffs.
Impacts and governance
The ecological and societal impacts depend on whether the drive is designed for population suppression or population modification. Suppression drives aim to reduce or eliminate target populations such as disease-vector mosquitoes, a strategy discussed in connection with malaria control in parts of sub-Saharan Africa where Anopheles species are central to local ecology and human health. Modification drives seek to spread traits that block pathogen transmission while leaving populations intact. National Academies of Sciences, Engineering, and Medicine has emphasized phased testing, risk assessment and robust monitoring as essential safeguards, and the World Health Organization has called for meaningful community engagement in regions where field work might take place.
What makes CRISPR drives unique is their potential to propagate beyond a single release site across connected populations and the consequent need to weigh environmental, cultural and territorial values alongside scientific evidence. Technical parameters such as conversion efficiency, resistance formation and population connectivity interact with human governance choices to determine whether a drive remains contained, spreads locally, or alters ecosystems at larger geographic scales.
