The 1990 science fiction novel and the hit film franchise Jurassic Park popularized the idea that amber could keep soft tissues and even DNA molecules intact for tens of millions of years. But actual attempts to extract DNA from amber or similar substances have so far failed, and samples embedded in the resin have been deemed unsuitable for genetic testing.
Unlike film, fossil tree resin is not a good choice for preserving DNA, a fragile molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms. When a viscous substance catches a small animal, the soft tissue begins to decompose immediately and most of the DNA is lost before the whole animal is even encapsulated. Even if some DNA is preserved, the chemicals in the resin will react with it, destroying it over time.
In 2020, a study published in the journal PLOS ONE sought to determine whether and for how long the DNA of insects enclosed in resinous materials can be kept. The researchers collected small ragweed beetles that were caught in the resin of amber trees (Hymenaea), a species endemic to the island of Madagascar. The chemical composition of this modern tree resin is very similar to fossilized amber. The samples were kept for 2 to 6 years and then processed.
The study found that although it was very fragile, the DNA was still stored in the samples. However, the first attempts to use ethanol to dissolve the resin around beetles proved to be counterproductive. Alcohol reacts with the resin, destroying any DNA. This observation may explain why previous attempts to extract DNA have always been unsuccessful.
Even after the extraction process was improved and the chemicals changed, new problems arose. The polymerase chain reaction is widely used to replicate small fragments of DNA, but the researchers found that this method is not very effective with DNA extracted from resinous materials. The substances found in the resin may inhibit the chemicals used to copy individual strands of DNA. Only after carefully cleaning the samples and repeating the PCR process several times was enough DNA replicated to study the genomics of the embedded organism.
It is not yet clear how long any genetic material inside the resin can survive. The researchers hope to apply the new method to other examples of soft tissue embedded in the resin and thus determine the rate of DNA degradation. Water also seems to play a key role in its conservation potential. The resin creates a waterproof barrier, keeping moisture in the soft tissue. This could affect the stability of the genetic material.
Surprisingly, recent discoveries suggest that DNA traces can be preserved even in rock.
In 2021, a team of scientists from the Institute of Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the Shandong Tianyu Museum of Nature successfully identified DNA-like molecules, preserved in cells 125 million years ago, on a old dinosaur fossil.
The dinosaur, named Caudipteryx, was a small, peacock-sized omnivore with long tail feathers. It roamed the shores of shallow lakes in Liaoning Province during the early Cretaceous, Forbes said.
“Geological data have accumulated over the years and have shown that the conservation of fossils in Jehol Biota has been exceptional due to the silicon-rich volcanic ash that buried the carcasses and kept them at the cellular level.Said LI Zhiheng, a professor and co-author of the study, published in the journal Communications Biology.
The scientists extracted a piece of articular cartilage from the right femur of this specimen, and used various methods of microscopy and chemistry to analyze it. They realized that all the cells had been mineralized by silicification after the death of the animal. This silicification is most likely the one that allowed the excellent preservation of these cells.
Furthermore, the team isolated some cells and stained them with a chemical used in biological laboratories around the world. This violet chemical, called hematoxylin, is known to bind to cell nuclei. After staining the dinosaur material, a dinosaur cell showed a purple core with darker purple threads. This means that the 125 million year old dinosaur cell has such a well-preserved nucleus that it retains some original biomolecules and chromatin wires.
Chromatin in the cells of all living organisms on Earth is made from well-packaged DNA molecules. The results of this study thus provide preliminary data suggesting that the remains of the original dinosaur DNA may still be preserved. But to test this accurately, the team needs to work much harder and use chemical methods that are much more refined than the coloring they used here.
“Let’s be honest, we’re obviously interested in fossilized cell nuclei because that’s where most of the preserved DNA should be. “, said the author of the study, Alida Bailleul. In 2020, she published another study that reports exceptional nuclear and biomolecule conservation in the cartilage cells of a Montana dinosaur.
“So we have good preliminary data, very interesting data, but we are just beginning to understand cell biochemistry in very old fossils. At this point, we need to work harder. ”
Despite their optimism to add this type of analysis of very old DNA to more common methods – such as DNA recovered from bone material, mummified and frozen tissues from much younger fossils, researchers have no intention of cloning. dinosaurs in the near future, probably for obvious reasons we’ve seen in the Jurassic Park franchise movies.
It is difficult to clone a dinosaur because there are no more compatible species carrying dinosaur embryos, but even if it were born, a dinosaur would not be able to adapt to our age due to lower oxygen levels and temperatures. smaller.
It was discovered that the Earth’s atmosphere 80 million years ago had 50% more oxygen than modern air. Even modern humans could not survive in the Jurassic age because of their high oxygen levels. Dinosaurs lived in a different ecosystem in the Triassic, Jurassic and Cretaceous, and today’s ecosystem, totally comfortable for mammals, is far too altered.
Today’s technology can’t bring the mammoth back to life either.
To date, no viable mammoth tissue or its intact genome has been found to attempt cloning. According to a research team, a mammoth cannot be recreated, but an attempt will eventually be made to invent an “artificial belly” in which a hybrid elephant embryo will grow with some woolly mammoth features.
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