Jurassic Park

Jurassic Park is a novel written by Michael Crichton and published in 1991, which was later adapted as a movie directed by Steven Spielberg. Written as a cautionary tale on unconsidered biological tinkering (in much the same spirit as Mary Shelley's Frankenstein), it explores the consequences of an attempt to re-create certain species of dinosaur to serve as amusement park attractions.

Biological issues

During the movie's production, the effects supervisors acknowledged that the Velociraptors featured in the movie were sized more like the larger Deinonychus. However, during the filming of the movie, paleontologists came across a larger dromaeosaurid species named Utahraptor, and the larger raptors remained.

Related Topics:
Deinonychus - Dromaeosaurid - Utahraptor

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The Dilophosaurus in the movie is smaller than their 6 m (20ft) real-life counterparts, and have a totally speculative frill like the Australian frill-necked lizard and the ability to spit venom. The spit and frill in particular were simply added for dramatic effect.

Related Topics:
Dilophosaurus - Australian - Frill-necked lizard

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Though the movie's theory that the Tyrannosaurus rex would be unable to 'see' someone if they were to remain still, some argue that it would still be able to smell them. In addition, most paleontologists consider Jurassic Park's use of the "amphibian visual cortex" here to be inaccurate, and that the dinosaur would be able to perceive static prey. This is acknowledged in the book: a character attempts to evade a tyrannosaur by freezing. This tactic fails and is criticized by paleontologist Richard Levine.

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Biotechnological background

The dinosaur DNA is extracted from fossilised mosquitos, and this small amount is then amplified by polymerase chain reaction (PCR). This has been done before, for example with a Cretaceous weevil in Cano et al. (1993) (no dinosaur DNA was found).

Related Topics:
Fossilised - Polymerase chain reaction

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There are some problems with this approach:

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• Foremost, the DNA featured in the movie is said to be from mosquitoes enclosed in Dominican amber. Dominican amber is approximately 30 million years old. Dinosaurs died out 65 million years ago.
• None of the dinosaurs featured in the movie are known to have existed in the Dominican Republic 65 million years ago.
• The mosquito had to have had just one species of dinosaur as its prey to avoid a mix-up
• It is unknown which dinosaur the sample contains. It would be impossible to tell which "species" it is, because the DNA sequences would fit somewhere between that of birds and crocodiles. The book does address this, stating that they "just grow it and find out" to Malcolm's annoyance.
• The dinosaur DNA has to be correct (it has to contain every chromosome) and should contain no gaps.
• The DNA is mixed with mosquito DNA. PCR is extremely sensitive, and will amplify that too.
• Present day PCR can't amplify large quantities of DNA (the entire dinosaur genome). Even if this was possible, it would take a very long time.
• PCR needs parts of the DNA to start the reaction (the so-called primers). To get them, the genome needs to be mapped beforehand.
• Because DNA is broken down by nucleases and proteolytic enzymes in the mosquito gut, the mosquito would have to be preserved immediately after feeding.

Furthermore, in the fossilisation process, molecules are altered. Nevertheless, amber is the best preservative, because organic material is preserved. But DNA cannot survive completely without gaps for tens or hundreds of millions of years.

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Tens of thousands of DNA base pairs were recently sequenced from 40,000-year-old skeletal remains of cave bears without using PCR, establishing that, in principle, large-scale genomic sequencing of fossilized remains is possible. Of course, the remains used in this study are orders of magnitude younger than anything from the dinosaur era, and the technique might not extend to those creatures.

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In the book the gaps in the DNA are filled by hybridizing the DNA with frog DNA. This is extremely difficult, as one would need to know which dinosaur genes are homologous with frog genes. The use of frog genes is probably a plot device, to allow some females to change sex and breed nevertheless (although natural sex change is also possible in some more advanced vertebrates).

Related Topics:
Genes - Homologous - Plot device - Vertebrates

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The next step would be bringing the DNA strands to expression. For that, one would need to inject the dinosaur DNA into the nucleus of a fertilized egg cell of a close relative of dinosaurs (birds or crocodiles (not frogs)). This technique is based on reproductive cloning, which was used to clone Dolly. In the movie, ostrich eggs are used for this purpose. However, the development of an embryo is regulated by hormones in the egg/uterus and the environment. These (bird or crocodylian) hormones need to have the same effect as their original dinosaurian counterparts. For that, they have to recognize particular pieces of dinosaur DNA, which they could hardly do. New research in plastics, however, has allowed for the creation of synethic eggs to nurture embryos through their development regardless of species. Extra hormones are needed from the original parent specimen, however, or constructed precisely from using the genome in order for the embryo to flourish.

Related Topics:
Nucleus - Reproductive cloning - Dolly - Ostrich

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