An international team of scientists has discovered ancient fossil chromosomes preserved in a vitreous state in the skin of a 52,000-year-old female woolly mammoth.
They uncovered a treasure trove of genetic data about the colossal mammal that some are trying to bring back from extinction, IGN reported.
"We knew that small fragments of ancient DNA could survive for a long period of time," said Dr. Marcela Sandoval-Velasco of the Center for Evolutionary Hologenomics at the University of Copenhagen and co-author of the new study detailing the discovery.
"But what we have found here is a sample in which the three-dimensional arrangement of these DNA fragments has been frozen in place for tens of millennia, thus preserving the structure of the entire chromosome," she added.
Chromosomes are filamentous structures composed entirely of DNA that are found in the cells of all living things. Each of these biological databanks contains a wealth of genetic information that scientists can use to gain insight into the history and evolution of life on Earth. Under normal circumstances, the remains of dead creatures break down over time, leading to DNA fragmentation. For this reason, most of the DNA of ancient animals discovered so far is incomplete, often consisting of fewer than 100 base pairs out of the billions that once made up the complete sequence of an organism before it decayed.
The base pairs - or letters - themselves are made up of combinations of organic molecules called nucleotides that link together to form the "rungs" in the ladder-like double helix structure of animal DNA. When viewed in the context of their surrounding structure, these combinations of bases can be analyzed to reveal a wealth of genetic information about long-extinct animals, assuming enough of the DNA has survived to the present day.
The 52,000-year-old skin that forms the basis of the new study, published in the scientific journal Cell, was taken from the ear of a mammoth whose remains were discovered in northern Siberia in 2018. Intensive analysis of the sample revealed the presence of complete fossil chromosomes in the ancient remains - each a billionth of a meter long - that had seemingly been frozen in a vitreous state for tens of thousands of years.
"This is a new kind of fossil, and its scale is smaller than that of individual ancient DNA fragments - a million times more sequence," explains Erez Lieberman Aiden, a co-author of the new study who is director of the Center for Genome Architecture at Baylor College of Medicine. The researchers were able to use sophisticated tools to reconstruct the three-dimensional genome architecture of the mammoth, while revealing the existence of small "chromatin" loops in chromosomal structures that are less than 50 nanometers long. | BGNES
