Mulleted mammoth named Chris Waddle helps scientists crack the creatures’ genetic code | Science

Researchers have reconstructed the genetic code of the woolly mammoth in unprecedented detail after discovering fossilized chromosomes in the skin of a 52,000-year-old carcass preserved in the permafrost of Siberia.

The mammoth’s luxuriant mane led researchers to name it after Chris Waddle, the mulleted former England footballer. It was freeze-dried after death, a process that preserved the 3D structure of chromosomes in the animal’s skin.

Armed with the ancient genetic material, scientists were able to piece together the mammoth genome, determine that the animal has 28 pairs of chromosomes and see which genes were turned on and off. These details are crucial to understanding what it means to be a mammoth.

Prof. Erez Lieberman Aiden, director of the Center for Genome Architecture at Baylor College of Medicine in Houston, said the samples were “a new kind of fossil” that “preserved biomolecules over vast periods of time” and contained much more information than previously studied samples.

Dr. Olga Dudchenko, also at Baylor, said the discovery of fossil chromosomes was a “game changer” because knowing the shape of an organism’s chromosomes made it possible to piece together the complete DNA sequence of an extinct creature, providing insights into their biology that were previously out of reach.

Scientists believe the animal’s skin spontaneously freeze-dried shortly after its death. Photo: Love Dalén/Stockholm University

The international team of researchers tested dozens of samples over five years before finding gold in a piece of skin taken from behind the ear of a mammoth unearthed in northern Siberia in 2018. They believe the animal’s skin spontaneously freeze-dried shortly after its death, preserving the tissue through a process similar to that used to make beef jerky.

The mammoth was named Chris Waddle after scientists recovering the carcass noticed its impressive mane. “It’s not clear if it’s exactly the same hairstyle the mammoth had when it was alive,” Dudchenko said. “And it turned out later that the mammoth was a female.”

Analysis of the skin revealed that the 3D structure of the mammoth’s chromosomes was preserved in the dehydrated cells after they had turned into a tough, glassy material. Once formed, the fossil samples, dubbed chromoglass, could last for millions of years, the researchers wrote in the journal Cell. In a series of unusual tests, the researchers showed that the DNA could survive in tissues that had been run over by a car, hit by a baseball or struck by a shotgun.

Until now, ancient DNA recovered from extinct species has been highly fragmented. The fragments allow scientists to detect small genetic differences between extinct animals and their living relatives, but little else. The new samples, by contrast, contain hundreds of millions of letters of code, revealing the large-scale structure of the genome.

Not only were the scientists able to assemble the mammoth’s genome and count its chromosomes, but they also found that the arrangement of the chromosomes in the cells revealed which genes were activated, including genes linked to woolliness and cold tolerance.

The work bolsters plans to bring back the woolly mammoth, a feat researchers hope to achieve by rewriting the genome of an Asian elephant to match that of a mammoth. “Is it enough for de-extinction? Probably not,” said Prof Marc Marti-Renom of the National Centre for Genomic Analysis in Barcelona. “There’s still a lot of work to be done if someone wants to turn a modern elephant into a mammoth. This is a step forward in that direction.”

The researchers hope to find more fossil chromosomes in other extinct species and in Egyptian mummies, many of which may already be in museum collections.

Prof Adrian Lister, a mammoth expert at the Natural History Museum who was not involved in the research, called the research “astonishing”.

“Research on ancient DNA has so far relied on a ‘soup’ of small fragments of DNA extracted from ancient tissue,” he said. “The researchers have been able to, in the case of this mammoth carcass preserved in Arctic permafrost, recover intact chromosomes with their DNA and the chromatin protein essential for their function intact.”

He added: “This new work opens up important new avenues for investigating the biology of extinct species. This exceptional preservation can be found in fossils much older than the 51,000-year-old mammoth, going back 2 million years, opening up the possibility of investigating the biology of much older extinct species and their relationships to and differences from living relatives.”

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