CLONING DINOSAURS

Follow the method seen in Jurassic Park to extract dinosaur DNA and decipher the true science from the fiction

THE TRAPPED MOSQUITO

1 Amber is fossilised tree resin, which has been known to preserve small organisms. To become preserved, an insect would have to have died as the resin hardened around it, or have been completely covered in the resin soon after its death. Buried in sediment, resin hardens under the extreme pressure and heat. Amber dehydrates the organism inside, which helps to slow its decay. It also serves as a protective shell, and as it hardens creates a perfect imprint of what’s trapped inside. Insects are small enough to be encapsulated, but how would a dinosaur’s DNA end up in this resin? The idea behind the mosquito in Jurassic Park is that only the genetic material from the dinosaur needs to be preserved. Mosquitoes existed at the same time as dinosaurs, and it’s possible that a mosquito with dinosaur blood inside it could have become trapped in resin. However, over time blood will decompose, and scientists have found that this material doesn’t preserve DNA as well as harder outer tissue.

CELL SURVIVAL

2 Bones and teeth are relatively common finds when it comes to dinosaur hunting. But what about the soft tissue needed for cloning? Soft tissue, containing gene-packed living cells, is the first thing to vanish when fossils are forming. Palaeontologists used to accept that the survival of any soft tissue over the course of millions of years was impossible, but in recent years unlikely discoveries have suggested otherwise. In 2005, Mary Schweitzer discovered small amounts of protein inside the leg of a T. rex in Montana. This showed how new discoveries can redefine what is possible.

MAKING A STRAND

3 In order to clone an animal with all the same physical features, a complete genome needs to be retrieved. For animals that are still alive, or died out more recently, collecting this information can be simple. Any potential dinosaur DNA that has been discovered at present has been in small fragments. This is due to a combination of ultraviolet light, cosmic radiation and enzymes breaking down proteins.

THE FROG ADDITION

4 As the DNA source is unlikely to be complete, is there any way of replacing the material that has been lost? Without further supplies of dinosaur DNA, the story of Jurassic Park involves replacing missing fragments with frog DNA. The use of frog DNA was vital to the plot for population control. Some frog species can undergo a biological change from female to male in order to breed when their species is under threat. This trait was passed to the dinosaurs. In reality, as frogs are amphibians, they are entirely different to dinosaurs, and their DNA is nowhere near similar enough. Birds, on the other hand, are descended from dinosaurs, and may have significant similarities. The best hope for palaeontologists who want to bring back dinosaurs is to wait for a well-preserved, large DNA sequence to be found.

CREATING COPIES

5 One method that can be used to create multiple copies of small DNA fragments is a polymerase chain reaction. Using a heat-resistant enzyme, a strand of DNA can be copied, producing millions of identical strands and providing a sample large enough for the order of amino acids to be analysed and sequenced.