A fossilized chromosome offers incredible insights into the Ice Age beast.
As biotech startups develop ways to resurrect the woolly mammoth, an international team of scientists have now reconstructed the iconic Ice Age beast’s 28 pairs of chromosomes.
This genetic breakthrough was possible due to a chromosome extracted from 52,000-year-old mammoth that luckily freeze-dried soon after death in northeastern Siberia.
 |
| MARK GARLICK/SCIENCE PHOTO LIBRARY//Getty Images |
This fossilized chromosome is the first of its kind and provides unprecedented details about the woolly mammoth’s genome as well as its genetic relation to its closest living cousin, the Asian elephant.
Although the idea of resurrecting long-dead animals really went mainstream with 1993’s Jurassic Park, most talk surrounding de-extinction revolves around a different icon of the not-so-distant past—the Woolly Mammoth. And although John Hammond was misguided in a lot of ways—don’t put man-eating animals in your theme park, for example—he did get one thing right: to bring back an animal from oblivion, you need genetic information. And lots of it.
In the case of the woolly mammoth, ancient remnants of DNA have been found buried in fossils recovered from Earth’s frozen tundra, but this information contains only around 100 base pairs, which isn’t nearly enough to get a full genetic picture of this majestic pachyderm. But a new international study, spearheaded by researchers at Rice University, have successfully uncovered a fossilized chromosome from a 52,000-year-old mammoth that was essentially freeze-dried after it died in what is now Siberia. Instead of containing the usual 100 base pairs, this chromosomal discovery is upwards of a million times longer and shows both how the genome was organized in living cells and what genes were active in its skin tissue. The results of the study were published in the journal Cell.
“Fossil chromosomes are a game-changer,” Baylor University’s Olga Dudchenko, a co-author of the study, said in a press statement. “Knowing the shape of an organism’s chromosomes allows us to assemble the entire DNA sequence of extinct creatures, enabling insights that were previously impossible.”
Unsurprisingly, the team discovered that the woolly mammoth contained 28 pairs of chromosomes, the same number as modern Asian elephants, and that active genes in the skin promoted the growth of hair follicles, giving woolly mammoths their hairy coat.
“For the first time,”Marc Marti-Renom, a researcher at the Centre Nacional d’Anàlisi Genòmica in Barcelona and co-author of the study, said in another press statement, “we have a woolly mammoth tissue for which we know roughly which genes were switched on and which genes were off. This is an extraordinary new type of data, and it’s the first measure of cell-specific gene activity of the genes in any ancient DNA sample.”
Scientists were able to create a 3D model of the chromosomes without relying on existing elephant data. That’s largely due to the fact that the opportune freeze-drying process preserved the chromosomes in a glass-like state, meaning individual DNA fragments couldn’t move far, and their structures were preserved across biological epochs.
Then, the team used a technique known as “Hi-C” that allows researchers to detect what parts of the DNA interact with one another in the nucleus, a process that Marti-Renom describes as trying to solve a three-billion-piece puzzle without even having a picture of the final image to look at. Finally, the researchers put this data together along with DNA sequencing to create a map of the woolly mammoth’s genome.
Although biotech startups are eager to resurrect the woolly mammoth, many experts have warned against trying to bring back the species, arguing that, at best, humans create an elephant hybrid that doesn’t really fit in the natural world or, at worst, we introduce an invasive species to the Arctic tundra. For now, this data will mostly help scientists better understand how genomes drive changing characteristics across different environments, but one day this chromosomal model could help resurrect the Ice Age icon.
Another positive? At least woolly mammoths don’t eat people.