A 700,000-year-old horse gets its genome sequenced
Scientists have just sequenced the oldest genome from a prehistoric creature. They have done so by sequencing and analyzing short pieces of DNA molecules preserved in bone-remnants from a horse that had been kept frozen for the last 700,000 years in the permafrost of Yukon, Canada.
June 26, 2013 — It is nothing short of a world record in DNA research that scientists at the Centre for GeoGenetics at the Natural History Museum of Denmark (University of Copenhagen) have hit. They have sequenced the so far oldest genome from a prehistoric creature. They have done so by sequencing and analyzing short pieces of DNA molecules preserved in bone-remnants from a horse that had been kept frozen for the last 700,000 years in the permafrost of Yukon, Canada. By tracking the genomic changes that transformed prehistoric wild horses into domestic breeds, the researchers have revealed the genetic make-up of modern horses with unprecedented details.The spectacular results are now published in the international scientific journal Nature.DNA molecules can survive in fossils well after an organism dies. Not as whole chromosomes, but as short pieces that could be assembled back together, like a puzzle. Sometimes enough molecules survive so that the full genome sequence of extinct species could be resurrected and over the last years, the full genome sequence of a few ancient humans and archaic hominins has been characterized. But so far, none dated back to before 70,000 years.Now Dr. Ludovic Orlando and Professor Eske Willerslev from the Centre for GeoGenetics have beaten this DNA-record by about 10 times. Thereby the two researchers — in collaboration with Danish and international colleagues — have been able to track major genomic changes over the last 700.000 years of evolution of the horse lineage.First, by comparing the genome in the 700,000 year old horse with the genome of a 43,000 year old horse, six present day horses and the donkey the researchers could estimate how fast mutations accumulate through time and calibrate a genome-wide mutation rate. This revealed that the last common ancestor of all modern equids was living about 4.0-4.5 million years ago. …
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