Jurassic Park taught us two things. 1) That T-Rexes can't see you if you don't move, and 2) resurrecting dinosaurs is a piece of cake that only needs a mosquito stuck in some sap.
Unfortunately, neither of these pieces of information is completely correct. Despite John Hammond's flashy video presentation, it seems we are still no closer to bringing dinosaurs back to this mortal coil.
"BINGO! DINO DNA!" - The Jurassic Park Theory
Jurassic Park's scene describing how InGen had resurrected the dinosaurs did seem to make sense. Broadly speaking, they claimed to have extracted dinosaur DNA from a mosquito which had become preserved in amber. The DNA was then sequenced with any missing gaps filled in with frog DNA. This DNA was then inserted into an ostrich ova in order to create an embryo, which was then transferred to special plastic eggs in order to hatch naturally. (These later stages are built upon outside of the movie).
Seems to make sense, right? Well, generally speaking the science is legitimate, but there are some major holes in the theory which, unfortunately, can't simply be filled in with frog DNA.
"That's One Big Pile of Sh*t" - Ripping Apart the JP Theory
Firstly, it would be incredibly difficult, if not impossible, to extract dino blood from a preserved mosquito. Scientists would need an extremely specific specimen - a female mosquito which had consumed a lot of blood - which considering the rarity of amber would be difficult.
Furthermore, many preserved mosquitoes are not of the same period as dinosaurs, while many still decompose from the inside out even when in amber. Additionally, even if they did find the perfect specimen, extracting DNA would still be a challenge, especially isolating the dino DNA from the mosquito's.
Experts now theorize that the most pristine examples of dinosaur DNA could come from preserved soft-tissue inside dinosaur bones. Recently, a team of scientists discovered what appears to be soft-tissue inside the bones of a T-Rex, something which was previously thought to be impossible. So far they have been unable to extract any DNA, but this might be a more promising route than mosquitoes trapped in amber.
It is also unlikely that adding frog DNA to the incomplete genome sequence wouldn't be of much use. Firstly, it is now thought that birds are much closer relatives of dinosaurs than amphibians, while splicing two DNA sets together wouldn't create a pure dinosaur, but simply a hybrid.
Furthermore, even researching what a complete dinosaur DNA sequence looks like is a feat currently outside the expertise and technology of scientists today. Sequencing the human genome took 13 years and even then the scientists who created it stated it could not be used for cloning.
The final major issue is that of the oocyte. In order for an embryo to gestate it must be inserted into an oocyte of the same (or extremely similar) organism. Since there are no dinosaurs today, there is no oocyte we could utilize. Birds and crocodiles have been suggested as alternatives, but they would not create the right eggs from which dinosaurs could develop, as each egg is specialized to that species.
Michael Crichton got around this issue by suggesting artificial eggs, but so far we do not have the ability to truly create these, or transfer the forming embryo into them.
"Clever Girl!" - Resurrecting Prehistoric Mammals
Experts have suggested, however, that techniques similar to those mentioned above, could be used to resurrect extinct prehistoric mammals which have died out in the last 10,000 years. Since these animals died out much more recently, there is an increased likelihood of being able to find workable DNA, while they also have close cousins which could potentially be used to gestate the fetus.
In fact, it has already been achieved. In 2003, a Spanish/French team of scientists managed to bring the Pyrenean ibex (a type of goat) back from extinction. They harvest cells from the last living ibex (who died in 2000) and artificially inseminated them into a hybrid Spanish ibex/goat. Unfortunately, the newly born clone only survived 10 minutes, although it proved the theory and the science was tenable.
With this experiment as proof, scientists believe they could bring back a whole menagerie of extinct critters, including the tasmanian tiger, passenger pigeon, sabre tooth tiger and the unique gastric brooding frog. However, the holy grail of de-extinction is surely the iconic wooly mammoth. Although these lumbering ice beasts were wiped out 10,000 years ago, scientists believe they’ve almost uncovered enough genetic material from the Siberian permafrost to make a cloning possible. Indeed, the biggest obstacle seems to be harvesting eggs from an Asian Elephant, a feat which has yet to be accomplished.
So, unfortunately, resurrecting dinosaurs is an accomplishment which is certainly bordering on the impossible, especially with our current capabilities. However, there is a relatively strong chance that we could potentially see prehistoric mammals return in our lifetimes - although that also poses a whole host of moral, ethical and practical questions.
In any case, San Diego can sleep safe for a while.