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Extinct Christmas Island Rat Genome Sequenced; Plans for De-Extinction

The genome diverges just 4.85 percent from modern Norway brown rats.

Photo by Oxana Golubets on Unsplash


  • DNA was extracted from “two dry preserved skin samples” that were “originally collected between 1900–1902 and held as part of the Oxford University Museum of Natural History collections,” according to the study.
  • The extinct Christmas Island rat’s genome was sequenced with >60x coverage.
  • Compared to the Norway brown rat (R. norvegicus), about five percent of the Christmas Island rat genome were completely unrecoverable.
  • An additional 1,600 genes were “recovered at lower than 90 percent completeness,” according to the study, and 26 genes were missing entirely.
  • The genes with missing information tend to be overrepresented in olfaction and immune response functions. Should this genome be used to “de-extinct” the Christmas Island rat, then, those missing genes would need to be added-in from the Norwegian rat genome.
  • “With current technology, it may be completely impossible to ever recover the full sequence,” Gilbert said for the press release, “and therefore it is impossible to ever generate a perfect replica of the Christmas Island rat.”
  • Next steps: Gilbert said he plans to use CRISPR to edit the black rat genome, and will attempt to change it into a Norway brown rat genome. If that proves successful, the gene-editing tools necessary for de-extinction could be applied to the Christmas Island rat.



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