JURASSIC PARK: A SCIENTIFIC REVIEW

 

ABSTRACT: Jurassic Park is a sci-fi piece where science seems to go further than fiction. The popular story of the dinosaur-themed park that goes from glory to disaster, plays with topics of molecular biology, genetic engineering, and biotechnology in such a way that it manages to blur the line between fact and fiction. In this review, the principal biotechnology-related points of the plot will be analyzed and compared with the bibliography to determine how feasible Michael Crichton’s story might be in real life. Therefore, some obstacles that keep Jurassic Park as a fictional story are the rate of DNA degradation, the method used to complete the genome, and the inaccurate lysine dependency. As can be seen, crucial details make the difference between reality and fiction. In summary, it was considered that most of the process that Dr. Wu used to create a dinosaur is plausible.

Keywords: DNA, biotechnology, cloning, genetics, sci-fi, dinosaurs.

 

INTRODUCTION

Science fiction is a genre that seeks to explore the possible implications of science and technology, whether real or imaginative, on society. This genre abounds in narratives related to time travel, robots, and aliens, but also about the consequences of technological progress in different fields [1], a topic explored in works such as Jurassic Park.

Jurassic Park is an adventure and science fiction film directed by Steven Spielberg and released in 1993, based on the homonymous novel written by Michael Crichton. The movie tells how an eccentric billionaire intends to build a dinosaur amusement park through technological advances in the area of genetic engineering; but also the catastrophic consequences that this implies for those involved and, possibly, for humanity.

Throughout this writing, an analysis of the fundamental points of the plot concerning biotechnology will be carried out, corroborating the application of real science and finding the details that lead it toward fiction.

 

ANALYSIS

The billionaire and philanthropist John Hammond aims to create an amusement park using dinosaurs as the main attraction. This was after he and a group of geneticists from his company InGen managed to clone dinosaurs from a fossilized DNA sample. However, after an incident with one of his workers, Hammond must prove the safety and viability of the project, so he will contact the scientists Ellie Sattler, Alan Grant, and Ian Malcolm to spend a weekend in his new park and thus know their professional opinion.

Unfortunately, Jurassic Park, located on the fictional Isla Nublar in Costa Rica, will be the scene where what started as a stroll turns into a constant fight to survive after a security breach allowed the dinosaurs to escape from their habitats.

 

1. What Makes Jurassic Park Extremely Believable

The following diagram shows the general procedure for cloning dinosaurs. All the information was taken entirely from the explanation given by Dr. Wu in the book since, unlike the film, the process is described in greater depth.

 

Figure 1. Cloning of dinosaurs [2].

 

1.1 First Argument: Extraction of Paleo-DNA.

In the book, Doctor Wu explains that, as shown in Figure 1, from a dinosaur blood sample found inside a fossilized mosquito in amber, it was possible to extract the genetic material directly from the erythrocytes presented. In Wu’s words, this was viable since red blood cells from dinosaurs, like those from birds, their closest evolutionary relatives, are nucleated cells. This makes obtaining the genome of these animals comparatively easier than that of a mammal.

Analyzing the above, Dr. Wu bases DNA extraction from erythrocytes on mentioning the evolutionary kinship shared by dinosaurs and birds. Carrying out research, in the bibliography, it is found that the dinosaurs are classified within the Archosauria, animals evolved from the captorhinids and giving rise to two lineages: the avian dinosaurs and the crocodilians; groups which are represented by the birds and crocodilians existing today [3]. Therefore, Dr. Wu’s account of its similarity to birds can indeed be recognized as valid.

In addition, there is evidence that extracting DNA directly from erythrocytes of a dino blood sample would be possible since, based on the fossilized remains that have been studied over time, it has been determined that dinosaurs must have presented nucleated erythrocytes, just like birds and reptiles, and unlike mammals [4]. 

Mammalian erythrocytes, like those of humans, do not have a nucleus. Therefore, to extract DNA from a mammalian blood sample, it should look for immunological cells, white blood cells, which do have a nucleus. However, the ratio of white cells compared to red cells is much lower; thus complicating the obtaining of the genome [5].

 

1.2 Second Argument: Completing the Genome.

Dr. Wu explained later that once the genetic material was obtained, it was subjected to sequencing to identify the molecule, find out its length and find out the sequence of nitrogenous bases that made it up. Once the DNA was sequenced, the book mentions that it was determined that the molecule had a length of 3 billion base pairs (3×10^9 bp). Also, the scientists realized that there were certain errors in the sequence, gaps where the DNA had degraded due to the passage of time. To solve this problem, geneticists took portions of various chains, either cleaved with restriction enzymes or broken by simple degradation, that matched the desired section to find out the missing amino acids.

The book also mentions how supercomputers were needed to carry out the sequencing since only these could support the processing of 3 billion pieces of data.

 

Figure 2. A simple example of a nucleotide sequence.

 

Analyzing what’s been said, the sequencing process refers to knowing the number and order of nitrogenous bases or nucleotides, Figure 2, that make up a specific DNA molecule. To carry out this task, high-tech equipment is used, which is capable of “reading” the nucleotides. It is essential to highlight the importance of sequencing since this is one of the approaches scientists can take to understand an organism [6].

The book also mentions how Dennis Nedry was hired to design a database for the supercomputers that perform the genomic sequence analysis, and how 3×10^9 of data was a colossal genomic length. However, much larger genomes have now been studied. The Australian lungfish holds the record for the longest documented genome to date, with an extension of 43×10^9 bp [7]; Another fairly extensive genome, and of a much better-known animal, is that of the axolotl or Ambystoma mexicanum with a length of 32 billion base pairs, which is currently being studied for its ability to regenerate itself, a field of much interest for medicine [8].

Considering that the previous genomes are examples of relatively small animals, it is possible to imagine that the genome of an animal as large as a dinosaur would be stratospheric. In other words, it is a common mistake to think that the more complex an organism is, the more extensive its genome should be; and yet, in the book the length of a dinosaur’s DNA chain is considered to be 3 billion base pairs, making the genomes of the Australian lungfish and axolotl at least 10 times larger, compared. However, it has been shown that there is no dependence between these two factors, an organism’s size, and its DNA length. Therefore, the decision to take 3×10^9 bp is not out of the ordinary. However, the DNA length mentioned in Jurassic Park can be considered a wink to humanity, since 3×10^9 bp is the very same length of the DNA molecule of the mammal with the greatest presence on the planet, the human being [9].

Once the genome sequencing was complete, Dr. Wu explained how fragments of the DNA strand, obtained by restriction enzyme cuts, were compared to fill in the gaps for the missing amino acids. In molecular biology, genetic engineering, and other related fields, these enzymes are used to fragment DNA in specific regions, since these enzymes are capable of recognizing specific sequences in the nucleotide chain and cutting right in that region [10]. This type of procedure, obtaining fractions of sequences and comparing them, is used in real life to characterize and identify microorganisms, since the pattern of cuts generated by the enzyme(s) used will always be the same for the same species of microorganism [11].

 

1.3 Third Argument: Phylogeny, Cloning, and Embryo.

Continuing with the tour, Dr. Wu, after several questions from Dr. Grant, talked about how only a small percentage of nucleotides vary from one species of dinosaur to another and that one way to identify each species would be to perform a phylogenetic analysis. But, due to the amount of time that these studies require, it was decided to opt for a faster procedure. Just to grow the products. To achieve it, a crocodile egg was used and the DNA was replaced; thus obtaining the embryo. Finally, the future dinosaurs were incubated under controlled environmental conditions.

Taking a closer look at what Dr. Wu said, a phylogenetic study is a diagram that represents the evolution of a particular species and its relationship with others, comparing characteristics that have evolved from a common ancestor. In addition, by knowing an individual’s genetic information, the phylogenetic analysis can be carried out in greater depth [12]. Therefore, in the hypothetical case of analyzing one or several individuals to find out their evolutionary proximity, phylogenetic analysis is a valuable tool since it can be compared with information that is already registered in a database or with previous studies. However, for issues that pertain to Jurassic Park, like working with extinct animals and no samples of the original DNA, this option becomes complicated. 

Finally, to obtain the embryo, it is mentioned how a crocodile egg is used to replace its genetic material with the dinosaur genome. This is a similar process to the one carried out to create Dolly the Sheep.

 

Figure 3. Cloning and the birth of Dolly [13].

 

As shown in Figure 3, Dolly was cloned from a mammary gland cell obtained from an adult bovine. This isolated cell was subjected to a nutrient retention process to induce a resting state. Consequently, it was fused with the help of electrical impulses with an unfertilized ovum, also of bovine origin. It is worth mentioning that the ovum used was previously subjected to the extraction of its nucleus, thus leaving only the original genetic material of the mammary cell [13]. 

Once both cells fused, this new cell began to divide, creating an embryo, which was implanted in a surrogate bovine womb. Finally, after the gestation period, Dolly was born in July 1996. This procedure of substituting the nucleus of one cell for another, and thus its genetic material, is known as Somatic Cell Nucleus Transfer (SCNT) and since then it has continued to be used in research and to generate clones of animals of different species [13].

 

1.4 Fourth Argument: Birth Control and Displacement Control.

After going through the laboratory, Dr. Wu invited Mr. Hammond and the rest of the guests to go to the nursery, where the newborn dinos were. This part of the visit led to more questions, curiosity, and concern from Dr. Grant. Alan asked about what happens when dinosaurs create nests and breed in the wild, to which Dr. Wu proceeded to explain the birth control methods applied to them.

Wu described that all the animals created in Jurassic Park undergo two strict controls. X-ray irradiation, to destroy gonadal tissue and sterilize them; and chromosome control, resulting in only female animals. 

Outside the lab, another concern crossed Ian Malcolm’s mind. What would happen if one of these animals reached the mainland? Before answering this question, Dr. Wu assured that the park has great security measures and that the distance that separates Isla Nublar from the nearest coast was more than 100 miles away. However, an additional measure to prevent the escape of the animals was to create them lysine-dependent. Wu explained that when designing the genome, he inserted a gene that creates a faulty enzyme in the protein metabolism. Resulting in dinosaurs being unable to produce lysine on their own, making them dependent on supplements given by the staff of the park. In this way, if one of the animals were found outside Jurassic Park, it would die in no more than 12 hours.

Summarizing this part, there are three controls to prevent either breeding or escaping in Jurassic Park. The breeding situation, explained Dr. Wu, should be solved by genetically creating female embryos and sterilization through radiation. Lastly, the dinosaurs should be contained by the park’s security and, in case of escaping, the lysine dependency should forbid them to survive beyond the facilities.

In the following, only the control by sterilization will be analyzed; since chromosomal control and lysine dependency will be developed in a further section, 2.2 Second Counterargument.

X-ray radiation was the second alternative mentioned by Dr. Wu. Radiation like this one causes damage to the body through ionization. This could be explained as the deposit of energy that produces the displacement of electrons from an atom of a molecule, and these ionized molecules may cause cellular death [14]. The response to radiation varies between tissues. The most sensitive cells are those which divide with more frequency and gonads are considered inside this group [15]. Therefore, the irradiation of the dino’s gonadal tissue should induce infertility in them. Hence, this fictional statement could be considered plausible, even when Dr. Wu underestimates its effectiveness.

 

1.5 Fifth Argument: Amphibian DNA and Sequential Hermaphroditism.

At half of the book, Dr. Grant makes an incredible but disturbing discovery. “It’s a velociraptor egg”. The dinosaurs in Jurassic Park were breeding. This fact represents one of the most important points in the plot and from now on this becomes a mystery in the story that is addressed in the final pages of the book. It turned out that during the creation of the dinosaurs, specifically while the geneticists were completing the DNA strain, Dr. Wu used amphibian DNA as material to fill the gaps in the sequence. The issue was that apparently, the portion of the amphibian genome that was transferred to the dinosaurs gave them the capability to change sex. Making them able to breed in the wild.

In real life, the individual’s ability to change of sex once it’s born does exist, and it is called sequential hermaphroditism. There are two variants of this phenomenon; protandry, when the change is from male to female, and protogyny, from female to male. This situation is presented in several invertebrate groups, crustaceans, and teleost fish [16].

The evidence suggests that for a species to adopt this kind of reproductive strategy, the sex reversal must provide a reproductive advantage after a certain point in the individual’s life. That is to say, an individual’s reproductive odds are better as one sex in earlier phases of their lives and better as the opposite sex after; allowing the individual to reach their maximal reproductive potential for a longer time in their life [16].  Nevertheless, even when sex reversal is employed as an advantage, this process entails physiological and behavioral costs that, for some species, could outweigh the benefits. For example, the populations of the species that carry out the sex reversal usually are characterized by sex ratios skewed toward the initial sex; which in turn can lead to a reduction in the effectiveness of natural selection, endogamy, and less genetic variability. These could be some reasons why sequential hermaphroditism is not very common [16].

 

2. Where the Fiction Resides

So far, this review has touched on key plot points that could be replicated in a real-life biotech lab. However, it is important to remember that even the smallest details could make a big difference. Now, it is time to point out the fiction.

 

2.1 First Counterargument: Fossils and the Passage of Time.

Going back to the fossilized amber there are some important elements to consider. Fossils refer to the distinguishable remains of living things on Earth in the past, such as bones, shells, impressions, and others. The problem here is how far in the past?

Dinosaurs were the dominant animals for around 100 million years, from the Late Triassic to the Late Cretaceous. The biggest dinosaurs, up to 80 tons, existed by the middle of the Mesozoic Period. Nowadays, dinosaurs have been extinct for approximately 65 million years [17]. Therefore, the newest dinosaur fossil that could be found would be from 65 million years ago. In addition, DNA is a fragile molecule. Once cells are no longer alive, DNA has limited chemical stability. The DNA molecule starts to degrade due to the effect of nucleases, microorganisms, and environmental conditions. The bibliography mentioned that, based on a mathematical model that predicts the grade of degradation of the DNA strain over time, even under a temperature of conservation of – 5 °C, there would be no bonds remaining in the DNA chain after 6.8 million years [18]. Thus, it is unlikely to obtain a fossilized dinosaur DNA sample preserved enough to be able to amplify.

 

2.2 Second Counterargument: Birth Control and Displacement Control.

During the tour through the lab, Dr. Wu mentioned three ways of controlling breeding and escaping in Jurassic Park. Chromosomal control, sterilization, and lysine dependency. In the past section 1.4 Fourth Argument, the second control method has been discussed already. Thus, chromosomal control and lysine dependency will be developed next. 

About the chromosomal or genetic control method, the bibliography shows that the only two archosaurian taxa present nowadays have different mechanisms to determine sex. Genotypic Sex Determination (GSD), when there is a chromosomal determination, for avians; and Temperature-dependent Sex Determination (TSD), when the sex differentiation depends on the temperature of incubation of the eggs,  for crocodilians. Furthermore, by the phylogenetic relation between crocodilians and dinosaurs, some studies suggest that these two could have shared the same sex determination mechanism [19, 20]. This means that the sex control that Dr. Wu proposes should be based on the temperature of the incubation of the embryos, not the chromosomal differentiation.

For the last control, Dr. Wu applied the lysine dependency, to prevent the dinosaurs from surviving on the mainland. Firstly, amino acids are the structural unit to create polymers called proteins and other essential substances with critical physiological functions. Amino acids are classified according to their nutritional requirement as essentials, the ones that need to be consumed, and nonessentials, the amino acids synthesized by the organism. In the essential amino acid group lies lysine [21]. That is, in reality, no animal species are capable of producing lysine by themself [22]. Lysine is indispensable in diets. Having said this, the approach that Wu proposed is incorrect.

 

2.3 Third Counterargument: Don’t move.

One of the most popular scenes of Jurassic Park is the attack of the T. rex. This happened once the tropical storm and the failure of security caused by Dennis Nedry were combined, and the T-rex escaped. Is at this point that Dr. Grant, in the movie, says his famous quote: “Don’t move. He can’t see us if we don’t move.”. Nevertheless, this is far from reality.

 Figure 4. Tyrannosaurus’s field of view [23].

 

A study conducted in 2006 mentioned that there is an important relationship between the binocular field of view (BFoV) and the predatory style that an individual presents. That is to say, the binocular overlap tends to be larger for those predators that use BFoV while hunting instead of prey detection by movement. For example, diurnal snakes need their prey to move to be able to detect it; contrary to other snake species that have around 20° more of binocular overlap. This is due to the larger BFoV, the better perception of the environment ahead of the animal as it chases prey. For dinosaurs like Tyrannosaurus the BFoV could vary from 35 to 55°, Figure 4, something comparable to modern hawks; and in the case of Velociraptor, the BFoV could reach 55 to 60°, similar to owls [23]. In addition, even when the BFoV is not the only parameter to consider, the Tyrannosaurus’s visual acuity is considered over 13 times better than human’s [23]. Therefore, a real-life T. rex would have definitely seen Dr. Grant.

 

CONCLUSION

Jurassic Park is a cinematographic and literary sci-fi phenomenon whose importance has been such that it has transcended for decades since its release. It is important to highlight that, besides its impact on pop culture, this piece of fiction brings the spectator closer to the scientific overview of genetics and biotechnology.

Throughout this review, the plot of Jurassic Park has been analyzed from a scientific point of view and it has been concluded that the processes or facts of DNA extraction from blood, completing the DNA strain by comparing different fragments, using SCNT to create a clone, sterilization by x-ray radiation, and the existence of animals capable of changing sex as an advantage for reproduction; are plausible in real life. On the other hand, the points considered as not-possible are DNA preservation after 65 million years, chromosomal sex control, and lysine dependency. In addition, the fact that dinosaurs had a vision based on movement is false.

Considering the above, the author concludes that the lack of paleo-DNA is the main obstacle to even considering trying to replicate Dr. Wu’s procedure; this is due to the other processes being real and adaptable, but without a DNA to amplify, cloning a dinosaur is just impossible.

To finish, this film, in the opinion of the author, has one of the best theses presented in the science fiction genre. From the mixture of real science and fiction with which arguments are created to the events that occur throughout the plot, An example of this is how genetics and molecular biology are used to support the structural pillar of this story: the cloning of dinosaurs.

 

ACKNOWLEDGMENTS

The author is grateful to the writers and directors who dedicate their lives to creating sci-fi stories like Jurassic Park, those stories that awaken wonder and curiosity. Thanks are also due to friends and acquaintances who took the time to read this writing and provide feedback . Finally, thanks to you reader for coming this far ♥.

 

 

 

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