Thylacines or Tasmanian tigers disappeared in 1936
Colossal Biosciences
The genome of the extinct thylacine has been almost completely sequenced, extinction company Colossal has announced. He claims the genome is more than 99.9 percent complete, with just 45 gaps that will soon be closed, but he has provided no evidence to back up his claim.
“It’s quite difficult to get the complete genome of almost any organism,” says Emilio Mármol-Sánchez at the University of Copenhagen in Denmark, his team. was the first to extract RNA from a preserved thylacine. For example, the last holdouts of the human genome were fully sequenced in recent years.
Thylacines, also known as Tasmanian tigers, were carnivorous marsupials once found throughout Australia, but by the time European explorers arrived, they were confined to Tasmania. The last known thylacine died in a zoo in 1936.
It was the genome of a preserved thylacine It was first sequenced in 2017 Using tissue from a 108-year-old thylacine pouch preserved in alcohol. However, this genome was far from complete, with many gaps. Now Colossal, which also aims to recreate the woolly mammothhe says that he has largely completed this genome with the help of additional DNA from a 120-year-old tooth.
“Our genome is not as complete as the most complete human genome, but we were able to take advantage of some of the same technologies,” says Andrew Pask, a member of Colossal’s scientific advisory board at the University of Melbourne in Australia.
It is difficult to completely sequence the genomes of plants and animals because there are large sections where the same sequences are repeated many times. Standard techniques that sequence small segments of DNA at a time do not work for these fragments; it’s like trying to reassemble a book from a list of rearranged words.
Newer Long Reading Techniques It can sequence much larger pieces of DNA – entire pages of the book. However, old DNA breaks up into many small pieces, so these methods often don’t help.
“Most ancient samples contain fragments of DNA that are tens of bases long, hundreds if we’re lucky,” says Pask. “The sample we were able to access was so well preserved that we could recover fragments of DNA that were thousands of bases long.”
Since there are no other thylacine genomes to compare to, there is no direct way to tell how complete it is; instead, Pask says Colossal is using other, related species in the same family to make that estimate.
But even if the genome is as complete as Colossal thinks it is it can really fill in the rest of the gapsthere is currently no viable way to create living cells with this genome. Instead, Colossal plans to genetically modify a living marsupial called a fat-tailed dunnart to make it more like a thylacine.
“It is more than a recreation of some characteristics”, says Mármol-Sánchez. “It would not be an extinct animal, but a rather strange and modified version of a modern animal that resembles our image of extinct animals.”
Colossal claims to have made a record 300 genetic modifications to the genomes of dunnart cells grown in culture. So far, these are all small changes, but Pask says the team plans to swap tens of thousands of base pairs of thylacine DNA in the near future. It’s not yet clear how many changes will be necessary to achieve the company’s goal of reintroducing the thylacine, he says.
When asked why Colossal did not provide evidence to support its claims, CEO Ben Lamm said the company’s only focus is on extinction, not writing scientific papers. “We’re not a paper-centric academic lab,” Lamm said. “We will continue to advance much faster than the scientific writing process.”
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