Jurassic Park (novel) - Biological Issues and Accuracy

Biological Issues and Accuracy

Scientists have argued that much of the book's content is impossible for various reasons, most notably the suggested means of recovering dinosaur DNA from mosquitoes trapped in fossilized tree resin. While this theory is largely a plot device by Crichton, both novel and movie sparked debate on the feasibility of cloning dinosaurs.

Four arguments why it would not be possible to obtain dinosaurs with this process are summarized thus:

  1. Research indicates dinosaur DNA would be very difficult to correctly sequence without a complete, intact DNA strand for comparison. It would be unlikely to find a complete sequence because DNA is typically unstable outside living organisms (unless it is in the proper buffer).
  2. Any gaps in the resulting DNA sequence must be filled with dinosaur DNA; using frog DNA as the story suggests would likely produce an organism that varied from the original animal, unless it was non-coding or DNA shared by both species (such as metabolic proteins) or DNA with highly conserved functions like homeobox genes.
  3. Cloning a complete DNA sequence requires an oocyte from the same organism. Since no Mesozoic dinosaurs are alive today, this is impossible. Though with new advances being made to genetic research, such as the creation of the supposedly artificial life Mycoplasma laboratorium project by the geneticist Craig Venter, artificially replicating an oocyte from recovered DNA or producing a suitable artificial one, is not necessarily beyond future technological capabilities. However it is still impossible at this time.
  4. The processes of CpG methylation and cytosine deaminization are especially important. The process of CpG methylation is a common regulatory device in eukaryotic DNA, where cytosine immediately preceding a guanine on the same strand is methylated. This acts as a molecular flag to control gene expression. The problem is, over time cytosine deaminization can occur—where a cytosine loses its amine group, which is replaced by a carbonyl group. Un-methylated cytosine results in uracil, which is not found in DNA, so can it be assumed to be a de-aminated cytosine. On the other hand, if the cytosine has methylated, then the product of deaminization is thymine, which is found in DNA—so it would be impossible to know which Ts are Ts, and which are de-aminated methyl cytosines.

Furthermore, it is likely that any prehistoric DNA obtained from a fossilized mosquito would have become contaminated with the mosquito's own, again making it problematic to clone an accurate and viable organism.

Crichton appears to have been aware of most, if not all, of the scientific objections raised, a consequence of his own medical background (having earned a medical degree from Harvard Medical School). Within the novel, Dr. Wu reflects on the nature of his dinosaurs. For Dr. Henry Wu, they are his creations, made from fragments of DNA available, and corrected and changed according to the needs of the client, Mr. Hammond. The animals replicated in this way would have represented a truly towering achievement in the biological sciences – the manufacture of fully synthetic organisms with structures based on theoretical models as opposed to truly observed biology. That the dinosaurs thus manufactured display the characteristics of natural organisms, including responding to environmental pressures (such as the all-female population, and lysinergic biochemical pathway degradation) increases the magnitude of the achievement.

A theme expressed throughout the story and its sequel is that of endothermic ("warm blooded"), homeothermic (able to maintain a stable body temperature), dinosaurs, a then-recent theory popularized by paleontologist Bob Bakker. While the cinematic adaptation of Jurassic Park used ostrich eggs as vessels to facilitate expression, the novel described "a new plastic with the characteristics of an avian eggshell." The plastic was called 'millipore', invented by an eponymous company subsequently bought by InGen. (Millipore Corporation is also the name of a real company that manufactures materials for use in biological sciences.)

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