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<\/div>Thylacines, or Tasmanian tigers, went extinct in 1936<\/p>\n
Colossal Biosciences<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
The genome of the extinct thylacine has been nearly completely sequenced, de-extinction company Colossal has announced. It says the genome is more than 99.9 per cent complete, with just 45 gaps that will soon be closed \u2013 but it has provided no evidence to back up its claim.<\/p>\n
\u201cIt\u2019s a fairly difficult thing to get a fully complete genome of almost any organism,\u201d says Emilio M\u00e1rmol-S\u00e1nchez at the University of Copenhagen, Denmark, whose team was the first to extract RNA from a preserved thylacine<\/a>. For example, the last few holdouts of the human genome were only fully sequenced in the past few years<\/a>.<\/p>\n Thylacines, also known as Tasmanian tigers, were carnivorous marsupials once found throughout Australia, but by the time European explorers arrived, they were limited to Tasmania. The last known thylacine died in a zoo in 1936.<\/p>\n The genome of a preserved thylacine was first sequenced in 2017<\/a>\u00a0using tissue from a then-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 mammoth<\/a>, says it has largely completed this genome with the help of additional DNA from a 120-year-old tooth.<\/p>\n <\/p>\n \u201cOur genome is not as complete as the most complete human genome, but we were able to take advantage of some of the same technologies,\u201d says Andrew Pask at the University of Melbourne in Australia, a member of Colossal\u2019s scientific advisory board.<\/p>\n 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 don\u2019t work for these parts \u2013 it is like trying to reassemble a book from a list of the words in it.<\/p>\n Newer, long-read techniques can sequence much larger segments of DNA<\/a> \u2013 whole pages of the book. However, old DNA usually breaks up into lots of small pieces, so these methods don\u2019t often help.<\/p>\n \u201cMost ancient samples preserve DNA fragments that are on the order of tens of bases long \u2013 hundreds if we are lucky,\u201d says Pask. \u201cThe sample we were able to access was so well preserved that we could recover fragments of DNA that were thousands of bases long.\u201d<\/p>\n Given the lack of any other thylacine genomes to make a comparison with, there is no direct way to tell how complete it is \u2013 instead Pask says Colossal is using other related species in the same family to make this estimate.<\/p>\n