Scientists at the University of California San Diego have created a new version of a gene drive which could lead to spreading specific, favourable genetic variants through a population. This “allelic drive” uses a guide RNA to direct CRISPR to cut undesired gene variants and replace them with better versions of the gene.

This will allow scientists to modify populations of organisms through precision editing of genes. This could see insecticide-resistant crops changed to increase sensitivity to them, or disease-carrying insects edited to make them less harmful.

Two versions of the allelic drive were set out in Nature Communications Journal: a copy-cutting version, where CRISPR is used to selectively cut undesirable genes, and a broader copy-grafting version, which promotes transmission of a favoured allele next to a site which is selectively protected from gRNA cutting.

So far the new technology has been demonstrated only in fruit flies, but also has potential for insects, mammals and plants. The scientists said several versions of the technology could be developed with combinations of favourable traits in crops to better sustain the world’s population. In mammals, the technology could better aid the development of new cures for diseases.

Annabel Guichard, first author of the research, said that editing using the drive could stop a “downward cycle” of increasing over-use of pesticides. She added: “An unexpected finding from this study is that mistakes created by such allelic drives do not get transmitted to the next generation…These mutations instead produce an unusual form of lethality referred to as ‘lethal mosaicism.’ This process helps make allelic drives more efficient by immediately eliminating unwanted mutations created by CRISPR-based drives.”