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According to Singularity Hub (This article and its images were originally posted on Singularity Hub January 2, 2019 at 10:05AM.)
In September 2018, a lab-based study published in Nature Biotechnology confirmed what many had long believed possible. The experiment involved cages of a few hundred mosquitoes, free to fly around and reproduce—but with a twist.
Half of the male mosquitoes had their genomes modified using CRISPR-Cas9. The genome modification made little visible difference to the males, but it rendered female mosquitoes infertile. Thanks to a technique known as a gene drive, the researchers were able to force this characteristic to be inherited by the offspring from the modified males. Within around ten generations, the gene drive had spread to the entire population; and, with all the females now infertile, “complete population suppression” followed. The mosquitoes in the cage were extinct.
Prior to CRISPR, genetically modified plants or animals would struggle to impose their modifications on a “wild” population in this way. As only one of the two chromosomes is modified, and each parent contributes one copy of the chromosome each to the offspring, the offspring has a 50 percent chance of inheriting an ordinary mutation.
In gene drives, the modified chromosome includes a string of CRISPR and guide RNA that shows the Cas9 protein where to cut. When it encounters an unmodified chromosome, it cuts the DNA around the modification. The cell then “repairs” the DNA by copying from the modified chromosome, including the gene drive itself. In this way, the gene drive ensures that it spreads into both chromosomes of any affected individual, and is passed onto any offspring they may have, efficiently spreading throughout the population.
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