CRISPR-Cas9 genome editing technology is transforming the way in which molecular biology is conducted. Genetic modifications can now be achieved with greater precision and far less cost and effort than was previously possible.

With genome editing, no foreign DNA is necessarily introduced in the process, so the resulting organisms may not be “transgenic”, per se. More controversial is the use of CRISPR-Cas9 technology as a tool for gene drive (=meiotic drive). 

For these applications, the CRISPR-Cas9 complex is introduced into the target species genome, and designed to duplicate and integrate itself wherever a specific genome sequence occurs. This effectively, and very efficiently, converts heterozygous progeny to being homozygous for the gene drive mutation.

An approach similar to this, using a less efficient homing endonuclease enzyme, is already being trialled to drive a sex ratio distorting mutation into vector mosquito populations. More recently, a CRISPR-Cas9 gene drive targeting the plasmodium responsible for malaria was published.

Applications for gene drives are now being proposed to achieve biodiversity and conservation outcomes, for example, to control invasive species or to make threatened species more resilient to the effects of climate change or disease.

Not surprisingly, concerns have been raised about the safety of this approach, and whether enough is known to predict unintended ecological consequences.