FREE ESSAY ON JURASSIC PARK; A POSSIBILITY?

JURASSIC PARK; A POSSIBILITY?

Introduction
The girl shrieks as the giant tree trunk of a leg crashes down shaking the earth. Her
screams are then drowned out by the prehistoric roar of the genetically engineered
Tyrannosaurus Rex as it searches for prey (Crichton, 1991). Everyone remembers this scene
from the best-selling novel by Michael Crichton, Jurassic Park. These scenes were then
brought to life by producer/director Steven Spielberg in the immensely popular movie by
the same name. Is this possible? As technological advances in molecular biology steam
into the twenty-first century, many scientists have found themselves asking this very
question. With continuing advancements in the methods of recombining DNA
(Deoxyribonucleic Acid), as well as the ability to read its genetic language, people have
started wandering just how science fiction these ideas really are.
There has been some limited success. DNA has been extracted and processed from some
extinct organisms. Single-celled organisms have even been "awakened" from a long
endosporic state, that do not exist in the same form in present times. The recent cloning
of the sheep "Dolly" at the Rosalin Institute in Scotland has served as a wake up call to
many as to the abilities modern biotechnology possesses (Currie and Psihoyos, 1996).
Assuming one had all the necessary means, would it be possible to create an extinct
organism with all the traits it once held? The answer seems to be yes.
The feasibility of such a thing does not seem too far-fetched when one considers the rate
at which science continues to break down barriers in all fields of study. So one final
question brought before researchers on projects such as this is: If we could recreate the
past through the recreation of long extinct animals, would we want to?
Fossils and DNA
Deoxyribonucleic acid (DNA) is the chemical basis of life (Campbell, 1996). All cells
contain the strands of sugar and phosphate. These strands are held together by the four
nucleotides; Adenine, Thiamin, Guanine, and Cytosine. Within these strands are millions
of genes. These are what forms the organism, makes it unique, in essence the blueprints
of life. DNA is eventually transcribed and translated into amino acids which carry out
the function outlined within the specific gene (Campbell, 1996). It is because of this
that many scientists have become skeptical of the ability of DNA to survive much more
than a few thousand years.
The viability of DNA is tested in this simple way. Amino acids, which are the building
blocks of proteins, come in both left-handed and right-handed forms. Most organisms build
proteins using left-handed amino acids known as L-enantiomers. After death, a chemical
process known as racemization begins changing L-enantiomers into right-handed
D-enantiomers until a balance is reached. Since racemization occurs at approximately the
same rate as DNA degradation, scientists can use the ratio of D-enantiomers to
L-enantiomers to determine the state of the organism's DNA. If extensive racemization has
occurred, the DNA has deteriorated. Researchers have not been able to obtain reliable
samples from remains in which the D-enantiomer content has reached ten percent. At this
rate, DNA should break up within a few thousand years in warm climates and 100,000 years
in cold climates (Monastesky, 1996).
This casts much doubt on the plausibility that resurrecting a long since extinct species
is possible. However, as it is not very plausible, it is somewhat possible. This could
happen if fossils were to be entombed under certain circumstances that did not allow
water, necessary for racemization to have access to the specimen(Monastesky, 1996).
The fossils that have been made famous by Crichton are those in which smaller organisms
happened to be trapped within tree sap, which later solidifies into the stone called
amber. These fossilized specimens are kept void of oxygen and water (Sykes, 1997). Large
amber quarries, such as the ones in the Dominican Republic, yield many fossils of this
kind every year. It is this fossil that will be the main focus of DNA extraction in this
paper.
These are the main culprits in the sudden race among geneticists to be the one to extract
and process the oldest DNA. To date, the oldest piece of isolated DNA came from a 125
million year old insect trapped within a bit of Lebanese amber by California Polytechnic
Institute at San Luis Obispo researcher Raul Cano (C.F., 1993). Analyzed, the now extinct
insect was found to resemble closest the modern day pine cone weevil. However, research
is underway to extract protozoa from a 225 million year old piece of amber obtained by
Robert Poinar at University of California at Berkely (Richardson, 1994).
Extraction
The extraction of DNA from a fossilized organism or piece of an organism must be a
completely sterile procedure. The contamination of any other type of organism, including
bacteria, could result in a faulty sample. The popular way of eliminating such potential
contaminants is using ultraviolet (UV) light. The UV rays mess up some of the chemical
components of DNA, effectively eliminating potential contaminating DNA. The sample is
shielded from such rays(DeSalle and Lindley, 1997).
The ideal specimen would be a piece of an animal, insect, or other organism preserved by
its natural surroundings. Examples of this would be the Mastodon dung discovered in
Florida in 1993 that was effectively preserved in sedimentary layers beneath a river bed
(AP, 1993), or the preserved remains of a saber-toothed cat that was recovered from the
La Brea tar pits in Los Angeles (Grimaldi, 1993). Both of these animals went extinct
somewhere between ten and fifteen thousand years ago. Unfortunately, in both cases, no
adequate DNA samples were recovered. Finding a fossilized specimen in these states with
intact DNA, as stated before, due to the natural degradation processes of organic
material is slim (Lewin, 1997).
The main focus of DNA isolation is on the various organisms found preserved within amber.
In the Crichton book, the suggested way of extracting DNA from an organism is to drill a
hole to the organism, and insert a needle (1991). However, this process in reality would
be very inefficient (Desalle & Lindley 1997). By doing this, the needle could
inadvertently pick up DNA from something else contained within the amber, or something on
the surface of the organism itself. A much more efficient way would be to crack the amber
in half at the site if the specimen. One would then proceed to remove pieces of the
organism (Cano 1996).
Upon dividing the specimen into individual cells, the cell and nuclear membranes must be
broken to get to the DNA contained within the nucleus. To accomplish this, the cells are
added to a solution with a soapy like detergent substance to dissolve the lipids in the
membranes and the enzyme proteinase to break down the proteins allowing access to the DNA
itself. The genetic material is then isolated using an ultracentrifuge. With this done,
the isolated DNA is entered into a thermocycle, fluctuating first hot then cold, along
with certain polymerase buffers and individual nucleotides. By fluctuating the heat, the
DNA breaks apart, then reforms. Through a process known as the polymerase chain reaction
which strings together the nucleotides creating a mirror image of the original DNA, the
DNA is multiplied exponentially until it reaches a desired amount (Gibbons,1994). The
multiple strands of DNA can be used to study evolutionary trends by comparing them to the
DNA of related modern organisms, or even attempting to clone a once extinct species.
Research
Bacteria
Bacteria are simple, unicellular organisms and are often used in genetic research because
of their haploid strand of DNA, and method of binary fission reproduction (Cano, 1996).
In binary fission, bacteria reproduce by exactly replicating their DNA and then splitting
in half. So in essence, bacteria clone themselves to reproduce. George and Roberta Poinar
discovered bacteria cells in the remains of the alimentary canal of nematodes preserved
in Mexican amber (Poinar, 1994). Bacteria would be a simple starting step for determining
a process for, isolating, testing, and replicating DNA of higher organisms in order to
eventually clone or study them. Unfortunately attempts to isolate ancient bacteria have
been inconclusive. The chief concern in isolating ancient bacteria is the contamination
of the sample by modern bacteria through fractures in the amber. Despite the extensive
sterilization techniques, scientists cannot be sure whether the bacteria isolated are
truly ancient bacteria (Poinar, 1994). For instance, Bacillus subtilis bacteria were
cultured from an amber from an amber specimen of a stingless bee from the Dominican
Republic, but these bacteria are commonly found in both the alimentary canal of the
modern-day stingless bee and in the soil. Also problems arise in extracting the DNA from
the single-celled organisms without accidentally destroying the small amount of genetic
material present (Richardson, 1994). Raul Cano continues studies of ancient bacteria at
California Polytechnic State University in San Luis Obispo (Poinar 1994). Cano became
famous recently for his reviving of a 600 thousand year old bacteria that was in an
endosporic state which kept it alive(Cano, 1996). Before this, Cano was brought into the
spotlight for extracting bacterial cells off an extinct bee which is estimated to be 40
million years old (Lewin,1995).
Insects
Insects are commonly preserved in amber after being caught in the sticky resin (sap)
emitted by some trees as a defense mechanism (Morell, 1993). In 1982, George and Roberta
Poinar identified intact cellular components such as nuclei, ribosomes, and chromosomes
in insects embedded in amber, but were unable to isolate DNA at that time (McAuliffe,
1993). The first successful DNA extraction was from an extinct termite, Mastotermes
electrodominicus, by a team at the American History Museum headed by David Grimaldi
(Grimaldi, 1993). These termites were found in amber from the Dominican Republic. This
species is defined by the large, fan-like lobe at the base of its hind wings and by its
many wing veins. The perplexity is that these characteristics are also given to
cockroaches, which evolved before Mastotermes electrodominicus; thus evolutionary lines
cannot be defined on such simple attributes and need to have more exclusive traits to the
species in order to establish the evolutionary unit. Another puzzle was the "missing
link" between termites and cockroaches: Is the Mastotermes closer related to termites or
cockroaches (Grimaldi, 1993)? Scientists are able to establish such links by doing
evolutionary comparison between ancient and modern DNA (Morell, 1993). Fragments of
mitochondrial DNA of Mastotermes were amplified using the polymerase chain reaction and
then linked to the modern-day termite, Mastotermes darweinis (McAuliffe, 1993).
Ancient DNA has also been extracted from stinglees bees being studied by Raul Cano and a
123 million year old extinct insect examined by George Poinar (Morell, 1993). The
fossilized insect that inspired the book and movie Jurassic Park has yet to be thoroughly
examined. This insect being a 125 year old biting midge found in a piece of Lebanese
amber. This insect could potentially have intact dinosaur DNA preserved within it
("Jurassic Bug", 1993).
Dinosaurs
Michael Crichton's book Jurassic Park introduced the idea of making dinosaurs from
ancient DNA preserved in amber to the public. In the words of Washington biotechnology
correspondent Jeremy Rifkin, "Jurassic park is the most massive exposure of
biotechnological research ever!" (Hamilton, 1993). Many scientists have done research
into the possibility of accomplishing this. Some say that it is impossible to recreate
dinosaur DNA because of the many gaps in the strands. Furthermore, any DNA recovered
would have to be from the gut of a blood-sucking insect that happened to perish in a pool
of sap almost immediately after feeding off of a dinosaur, (for it is very unlikely that
a dinosaur would be preserved in amber itself). Plus, the amount of DNA extracted would
be quite minuscule compared to what it takes to make a complete organism (DeSalle &
Lindley, 1997). In the book and movie, the holes in the DNA sequence are filled using
frog DNA, yet like critics say "too much frog DNA and your T-Rex Croaks" ("Are Movies
Science", 1996). In addition, the much more realistic gene donor would be the closer
related bird (Monastesky, 1994).
The easier way of extracting intact DNA would be to find preserved fossilized remains
with reliable DNA (Svitil, 1995). However, efforts to isolate DNA from fossilized bones
have been unsuccessful because most organic material is converted to inorganic compounds
in the fossilization process, and because of the exposure to air and water. Scott
Woodward of Brigham Young University in Provo, Utah, claimed to have extracted DNA from a
bone of a dinosaur from the cretaceous period 134 base pairs long of cytochrome b, but
controversy remains as to if the DNA belongs to a contaminant or to the actual dinosaur
(Gorman 1994). Using the amino acid racemization test, scientists found that the
percentage of D-enantiomers had reached 21 percent, which cast further doubt on the
authenticity of the DNA found (Monastersly 1996). Other claims, such as those made by
scientist Jack Horner, of the Montana State University Museum, who oversaw the extraction
of red blood cells from the fossilized leg of a Tyrannosaurus Rex which could contain
viable DNA by graduate student Mary Schweitzer have been widely disputed (Breo, 1993). No
claims have been greeted with a "warm welcome". This is mainly due to the fact that since
dinosaur DNA is unknown to science, being absolutely sure of what is being extracted is
almost impossible (Kiernan, 1993).
Assuming that scientists could actually obtain and isolate actual dinosaur DNA, and even
fill in the gaps in the DNA with that of another organism, with the intention of creating
an actual dinosaur, the problem that remains is how? In the cloning of "Dolly",
scientists, after inserting the genetic material into a fertilized egg, could input the
genetically altered egg into the womb of a surrogate sheep ("Are Movies Science", 1996).
To create a dinosaur, one would need to implant the material into an egg, derived of the
same species or at least similar. Since nothing is
known about dinosaur DNA, it would be impossible to distinguish a species. Also the lack
of information would make it hard to choose a host egg that provided the proper
environment for the dinosaur embryo (DeSalle & Lindley 1997). Even if one were able to
get past this somehow, and a dinosaur were hatched, how would we take care of it? So
little is known about dinosaur diets and behavior, that it would be very hard to
accommodate the creature (Waters, 1995). In addition, there are so many new and altered
diseases in the atmosphere at present time than there were in the times of the dinosaurs,
that it would be next to impossible to keep a free-roaming dinosaur healthy. The most
probable place a dinosaur would be kept would be in a sterile lab facility, much unlike
the park Michael Crichton created in his book (Lessum, 1993).
Yet however improbable, scientists continue on in their quest to create a dinosaur. "The
risk is well worth the end result," states George Poinar (Poinar, 1994). Indeed, the
recreation of a dinosaur would lead to remarkable new discoveries about their behavior,
eating habits, disease resistance, and quite possibly determine the reason for their
extinction, not to mention, amazing millions of little kids around the world.
Conclusion
Cloning ancient life forms like in the movie and book, Jurassic Park is a sequence of
"long shot" chances. The path from finding and sequencing suitable DNA, as well as
providing a host for growth and a suitable environment for it to function is beset with
many obstacles. Maybe after decades of extensive research in each of these areas, such a
project as recreating a dinosaur may be attempted, but most scientists agree that their
"extinction is permanent" (Paabo, 1993). Thus, cloning dinosaurs or any ancient organism,
remains a frontier of the future. However, as David Grimaldi writes, "While it is a long
way from amplifying a bit of DNA to reconstruct a whole dinosaur - or even a termite -
these new developments open up many exciting scientific possibilities" (1993).