Jurassic Park And Tech
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).