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Файл:Biotechnology (Биотехнология). Учебно-методическое пособие
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Designing bionanomachines from scratch is currently a great
challenge that is under intensive study in many laboratories. Ideally, we
want total control. For instance, we might want to build a “nanotube
synthase” that constructs carbon nanotubes of defined size and geometry.
We would like to be able to go to our computer and design a protein that
would fold into a stable structure, creating an active site that performs this
chemical reaction.
Unfortunately, there are gaps in our knowledge that must be filled
before this capability is possible. Today, we cannot reliably predict the
folded structure of a protein from its chemical sequence, and, given a folded
structure, we cannot consistently predict its chemical activity. But these two
steps are currently under scrutiny by scientists, with the firm expectation
that they will be solved in the foreseeable future. Then, true biomolecular
design will be a reality.
This chapter presents an overview of the many techniques that are
available for the design, synthesis, and analysis of biomolecules. This information is by no means comprehensive and provides only an introduction to
these powerful methods. Many excellent workbooks and recipes are
available for each of these methods59.
59
Мельникова, В.А., Барановская М.Е., Халикова Д.Г. Microbiology and
Biotechnology. Указ. соч.
121
Text 4. Principles of Biotechnology
Biotechnology Defined
Biotechnology can be broadly defined as "using living organisms or
their products for commercial purposes." As such, biotechnology has been
practiced by human society since the beginning of recorded history in such
activities as baking bread, brewing alcoholic beverages, or breeding food
crops or domestic animals.
A narrower and more specific definition of biotechnology is "the
commercial application of living organisms or their products, which
involves the deliberate manipulation of their DNA molecules" (see glossary
for definitions of bold-print words). This definition implies a set of
laboratory techniques developed within the last 20 years that have been
responsible for the tremendous scientific and commercial interest in
biotechnology, the founding of many new companies, and the redirection of
research efforts and financial resources among established companies and
universities. These laboratory techniques provide scientists with a
spectacular vision of the design and function of living organisms, and
provide technologists in many fields with the tools to implement exciting
commercial applications.
Principles of Biology
All living organisms are composed of cells that contain a substance
called DNA (deoxyribonucleic acid) in the chromosomes. The structure of
DNA molecules contains information that is used by cells as a "recipe" for
the organism; that is, the characteristics of any living thing essentially are
determined by the information in DNA. The "words" for the DNA recipe,
called genes, are derived from a 4-letter alphabet (A, C, G, T) and usually
contain between 1,000 and 100,000 letters. The entire recipe, called the
genome, may contain between 4 million (simple bacteria) and 3 billion
(human) letters or more.
Except for the sequence and number of letters in each recipe, DNA
from any organism is chemically and physically the same. One of the great
scientific discoveries of biotechnology is that DNA from any organism will
function if it is transferred into any other organism!
Using Biotechnology to Modify Plants and Animals
Combining DNA from different existing organisms (plants,
animals, insects, bacteria, etc.) results in modified organisms with a
combination of traits from the parents. The sharing of DNA information
takes place naturally through sexual reproduction and has been exploited in
plant and animal breeding programs for many >ears.
122
However, sexual reproduction can occur only between individuals
of the same species. A Holstein cow can be mated with a Hereford bull
because the two animals are different breeds of the same species, cattle. But
trying to mate a cow with a horse, i different species of animal, would not
be successful.
What's new since 1972 is that scientists have been able to identify
the specific DNA genes for many desirable traits and transfer only those
genes, usually carried on a plasmid or virus, into another organism. This
process is called genetic engineering and the transfer of DNA is
accomplished using either direct injection or the Agrobacterium,
electroporation, or particle gun transformation techniques. It provides a
method to transfer DNA between any living cells (plant, animal, insect,
bacterial, etc.). Virtually any desirable trait found in nature can, in
principle, be transferred into any chosen organism. An organism modified
by genetic engineering is called transgenic.
Products of Genetic Engineering
Specific applications of genetic engineering are abundant and
increasing rapidly in number. Genetic engineering is being used in the
production of pharmaceuticals, gene therapy, and the development of
transgenic plants and animals.
1. Pharmaceuticals. Human drugs such as insulin for diabetics,
growth hormone for individuals with pituitary dwarfism, and tissue
plasminogen activator for heart attack victims, as well as animal drugs like
the growth hormones, bovine or porcine somatotropin, are being produced
by the fermentation of transgenic bacteria that have received the appropriate
human, cow, or pig gene.
2. Gene Therapy. The first clinical gene therapy is underway to
correct an enzyme deficiency called ADA in children. Bone marrow cells
are removed, defective DNA in bone marrow cells is supplemented with a
copy of normal DNA, and the repaired cells are then returned to the
patient's body.
3. Transgenic Plants. Transgenic plants that are more tolerant of
herbicides, resistant to insect or viral pests, or express modified versions of
fruit or flowers have been grown and tested in outdoor test plots since 1987.
The genes for these traits have been delivered to the plants from other
unrelated plants, bacteria, or viruses by genetic engineering techniques.
4. Transgenic Animals, Presently, most transgenic animals are
designed to assist researchers in the diagnosis and treatment of human
diseases. Several companies have designed and are testing transgenic
mammals that produce important pharmaceuticals in the animal's milk.
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Products such as insulin, growth hormone, and tissue plasminogen
activator that are currently produced by fermentation of transgenic
bacteria may soon be obtained by milking transgenic cows, sheep, or goats.
Using Biotechnology in Diagnostic Applications
Since each living creature is unique, each has a unique DNA recipe.
Individuals within any given species, breed, or hybrid line can usually be
identified by minor differences in their DNA sequences - as few as one
difference in a million letters can be detected! Using the techniques of DNA
fingerprinting and PCR (polymerase chain reaction) scientists can diagnose
viral, bacterial, or fungal infections, distinguish between closely related
individuals, or map the locations of specific genes along the vast length of
the DNA molecules in the cells.
Identifying Organisms
By using RFLP technology (restriction fragment length
polymorphism), DNA fingerprints can be generated. Any individual
organism can be uniquely identified by its DNA fingerprint. Consequently,
this fingerprint can be used to determine family relationships in paternity
litigation, match organ donors with recipients in transplant programs,
connect suspects with DNA evidence left at the scene of a crime (in the
form of hair or body fluids), or serve as a pedigree for seed or livestock
breeds.
Identifying Genes
One important aspect of genetic engineering projects is to identify
the DNA gene that controls a particular trait. In the same way that a visitor
might use the state, city, street, and house number to locate a friend's house,
genetic engineers use genetic "maps" to locate genes. The genetic maps are
generated by statistical analyses, PCR, RFLP, and DNA sequencing. Maps
are being developed for humans, mice, swine, cattle, com, wheat, and other
plants or animals with commercial or research importance.
Diagnosing Infectious Diseases and Genetic Disorders Diagnosis of
infectious diseases is a profound application of the new DNA technology.
Tuberculosis, AIDS, papillomavirus, and many other infectious diseases, in
addition to the inherited disorders like cystic fibrosis or sickle cell anemia,
are diagnosed within hours by the PCR technique rather than days or weeks
by traditional methods60.
60
Мельникова В.А., Барановская М.Е., Халикова Д.Г. Microbiology and
Biotechnology. Указ. соч.
124
Text 5. Can Roses Be Mated with Pigs?
In response to the article on Biotechnology (PDI, 6/19/04), Dr.
Benigno Peczon, president of the Biotechnology Coalition of the
Philippines said that roses can't mate with pigs because "the sexual mode of
reproduction is limited by the compatibility in the number of chromosomes
(where the DNA is located). Thousands of genes are necessary from both
parents to form the DNA of offspring. Biotechnology identifies one or two
genes which encode some useful trait then adds the genes to another
organism's DNA so that the transfer of a few genes won't turn the pig into a
rose."
Returning to the subject of bio-engineering (if you prefer the more
proper term is "recombinant DNA technology," a mite too difficult to
pronounce), what it really means is that a foreign gene is spliced in the
DNA of an organism "so that when the organism grows, the new trait
encoded by the inserted gene is expressed." Insulin, for instance, is the
result of the splicing of a human gene, responsible for producing human
insulin, into the DNA of E. coli, a bacterium which produces insulin
identical to human insulin. As you can see there are benefits to be derived
that no one can argue. We are also told that biotechnology can improve the
safety of foods by taking out some harmful substances or adding beneficial
ones. Thus the GM peanut is being developed so that people who are
allergic to it may enjoy eating peanut spread or peanuts, period. Genetically
altered tomatoes would contain more lycopene which is believed to delay
the onset of cancer. Dr. Peczon explains that GM foods "are only as safe as
their conventional counterparts." And that GM foods currently in the
market contain no antibiotics.
This same technique is being used to produce modified food that
promises to increase production and to resist pests, disease, droughts; and
contains vitamins and nutrients severely lacking in the diets of the poor. If
this is the case, why aren't Third World countries embracing GM foods
without protest?
One of the things opponents of GM technology are asking is that
imported, genetically modified food items should be identified. According
to Dr. Peczon labeling GM foods would increase their price by around 10
percent, and their manufacturing costs by 11-12 percent. He asks "will the
price increase justify the fact that the labeling is not related to safety?"
Some people also ask: Is it safe to combine genes that have not previously
been combined, thus creating new traits-and do we know the long-term
impact on our biodiversity?
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Dr. Peczon cites figures showing "more than 3,500 scientists are
convinced of its safety as listed in the AgbioWorld website," Several
prestigious institutions, such as the World Health Organization and the
National Academy of Science, are convinced about the safety of GM foods.
European Commission-sponsored research studies, conducted by over 400
research teams, also attest that the GM products pose no threat to human
health or environment.
Another concern is: Genetic engineering is under the control of the
private sector; it is being developed almost solely by that sector. Since a
company's objective is to make money, one cannot expect them to be
concerned with the welfare of poor Third World countries more than
making a profit. The other question we have to ask is whether the
transgenic crops will tie the fanner to specific chemicals and a specific
company such as Monsanto? Genetically modified seeds cannot reproduce,
cannot be saved for the next year's crop. Moreover, the technology is
controlled by another country. What happens if you become dependent on
some crop or rice variety and the controlling country refuse to send the
seeds? In effect, there is no local control and therefore no food security.
There are people who are genuinely worried that these genetically
modified foods will contaminate and destroy local varieties, including the
wild species of local crop. We don't know. What tickles our curiosity is that
IRRI's miracle rice was supposed to increase production and make selfsufficient way back when. The hybrid rice is also heavily dependent on
fertilizers which has to be imported. The question is why are we still
importing rice?
Two issues/questions have also been brought up at protocol
negotiations and at World Trade Organization meetings. One is the right of
a country to know what it is importing and whether a government has the
right to refuse an import it considers unsafe for its population. On the other
hand, you should know that bio-engineering was introduced in 1996 and as
of 2003, GM crops have already been planted to 67.7 million hectares
across 18 countries. The Philippines started planting GM crops in 2002,
with only 126 hectares. But as of last year, the total land area planted to
such crops has gone up to 11,000 hectares; by the end of this year, it is
expected to reach 30,000 hectares. In case you wish to learn more about
GM crops, you can access Biotechnology Coalition's website at
www.bcp.org.ph61.
61
www.bcp.org.ph
126
Text 6. Biotechnology and Genetic Diversity Experts Say Risks and
Benefits of Biotechnology Must Be Weighed
on a Case-By-Case Basis
Could plant biotechnology affect wild ecosystems?
Critics fear a genetically enhanced gene could "escape" from a
farmer's field and breed with a wild relative to create a "superweed" that
could overwhelm the natural environment and curtail genetic diversity.
Proponents, on the other hand, say the productivity gains of
genetically enhanced ' crops allow more food to grow on existing farmland,
which preserves natural areas from being plowed under to feed a growing
population. This, supporters say, promotes genetic diversity.
Researchers increasingly say the question is no longer whether a
genetically enhanced gene, or transgene, will "escape." Pollen flow between
plants is a natural phenomenon that has been occurring for thousands of
years.
Indeed, a 1999 study found that 12 of the world's 13 most important
food crops hybridized with at least one of their wild relatives. As Klaus
Ammann, director of the botanical garden at the University of Bern in
Switzerland puts it, "I can assure you that pollen did not learn to fly with
the transgenes." So release of genetically enhanced genes is as likely to
occur as with conventional varieties.
But the better question to be asked is what could happen when
specific genetically enhanced genes do enter the natural environment, says
John Burke, a biology professor at Vanderbilt University in Nashville,
Tenn.
"Our work ... indicates a clear need to assess the relative risks and
benefits of genetic modification on a case-by-case basis," he wrote in a
paper titled, "Assessing the Risks of Transgene Escape: A Case Study in
Sunflowers."
While there is much to study, most experts have concluded that the
process of genetic engineering does not pose any unique risks to the
environment.
"So far, most scientific inquiry into the subject has failed to support
the notion that there is something about the genetic engineering process
itself that intensifies any threats from gene flow," states an August 2003
report titled "Have Transgenes, Will Travel," issued by the Pew Initiative
on Food and Biotechnology.
A panel of experts assembled by the National Academy of Sciences
reached a similar conclusion.
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"The genetic engineering process, per se, presents no new
categories of risk" to the environment compared to conventional breeding,
said the August 2002 report titled, "The Environmental Effects of
Transgenic Plants."
Background
Although there is no question that the natural process of gene flow
via pollination does occur, a number of conditions must be met:
First, there must be sexual compatibility between a domesticated
crop and its wild relative for gene flow to occur -just as a bird cannot
successfully mate with a frog.
Second, the plants need to be close enough so the pollen can move
from plant to plant (pollen from canola, for example, can travel farther than
pollen from corn).
Third, the plants need to flower at the same time.
In general, biotech crops that can easily hybridize with their wild
relatives could theoretically pose greater risks than those that don't,
explained Burke.
Because there are no wild relatives of corn or soybean in the United
States, for example, researchers say there is no chance for genetically
enhanced genes from either crop to breed with a wild relative. So the risk of
any ecological problems from these crops in the United States is very low.
But "there are wild relatives of corn in Mexico and wild relatives of
soybean in Korea and China. So the same crops can potentially pose
different risks of breeding with their wild relatives depending on where they
are grown. That's why experts like Burke say genetically enhanced crops
must be studied on a case-by-case basis.
Similarly, different genetically enhanced traits pose varying degrees
of risk. A gene for herbicide tolerance, for example, isn't likely to confer an
advantage to a plant in the wild because herbicides won't be encountered
there.
But other traits — such as resistance to pests, disease or hostile
growing conditions such as drought — could theoretically give a weedy
relative an upper hand, says Burke.
Burke studied sunflowers (which have been developed but not
approved for market) that have been genetically enhanced to resist white
mold, one of the most widespread diseases that can cause yield losses of up
to 70 percent. Because cultivated sunflowers are grown in regions where
wild sunflowers are common, Burke says "crop-wild gene flow is a virtual
certainty."
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But what he concluded was that although the transgene for mold
resistance was transferred to wild sunflowers, it "will have little effect on
the evolutionary dynamics of wild sunflower populations." It appears that
wild sunflowers already have resistance to white mold, so the additional
white mold resistance gene didn't allow them to survive any better.
Environmental safeguards
Before any biotech product reaches the market, the possible risks to
the environment are carefully analyzed, and safeguards — such as buffer
zones around the perimeter of fields planted with biotech varieties - are
required. A buffer zone is planted with traditional crop varieties to
minimize any possible effects of pollen flow to a neighboring farmer's field
or to a wild plant relative.
Farmers have long learned to keep different varieties of the same
crop separate. For example, rapeseed was originally grown in Canada to be
used as a lubricant because it has high levels of erucic acid, which can be
harmful when eaten. Conventional plant breeders developed improved
varieties of rapeseed - now called canola - with low levels of this harmful
acid. Canola is now a widely used cooking oil.
Both types of rapeseed are still grown in Canada. "Canadian
farmers and processors easily and routinely" keep these two varieties
separate, said Henry Miller, a fellow at the Hoover Institution and founding
director of the Office of Biotechnology at the U.S. Food and Drug
Administration.
Similarly, experts say new varieties of biotech corn could exist
side-by-side with their wild relatives in Mexico without posing a threat to
genetic diversity.
Corn in Mexico
Corn, or maize, is a cornerstone of society in Mexico, widely
considered the birthplace of corn. So news in a September 2001 issue of
Nature, a respected science journal, that traces of biotech corn had been
discovered in farms field in Oaxaca created widespread concern.
Nature later disavowed its original article, and several researchers
say biotech corn will not have a negative impact on traditional varieties.
"There is no scientific basis for believing that out-crossing from
biotech crops could endanger maize biodiversity," said Luis HerreraEstrella, director of the Mexico-based Center for Research and Advanced
Studies, which is known by its Mexican acronym, CINVESTAV. "Gene
flow between commercial and natural varieties is a natural process that has
been occurring for many decades."
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Some genetically engineered traits, such as built-in pest resistance,
could fold into traditional crop varieties and may help them survive better,
he said. Others will die out if they don't provide a recognizable benefit to
farmers or consumers.
The real threat to genetic diversity in Mexico, say many
researchers, is the exodus of small fanners who are leaving their small plots
in Mexico for more lucrative jobs in the cities of Mexico and the United
States. Since corn requires human intervention to thrive, unique varieties
are being lost when the plots are abandoned.
"The most important consideration in the loss of diversity has to do
with the fact that farmers are simply abandoning farming," Mauricio
Bellon, of the International Center for the Improvement of Wheat and
Maize (CIMMYT), told National Public Radio in December 2001.
Increasing genetic diversity
The exodus of rural farmers to cities is occurring at a rapid pace
around the world — not just in Mexico. So the genetic diversity of more
crops than corn is at stake.
At the same time, a growing world population, coupled with
increased urbanization and higher incomes, is creating a greater demand for
food. The United Nations predicts that the global population will increase to
8.9 billion by 2050 - a 40 percent increase over the 6.3 billion people on
Earth today.
By helping farmers produce greater yields, biotechnology can play
a part in making farms of all sizes more viable, which in turn could help
reduce the pressure on remaining wilderness areas.
Currently, about 38 percent of the Earth's land area is cropland or
pasture. To keep pace with growing food demand, the increase in natural
land converted to cropland or pasture has been about 0.3 percent — about
the size of Greece or Nicaragua — every year. By one estimate, an
additional 4 billion acres of arable land will need to come under the plow
by 2050 if there are no increases in farm productivity. That's more than
twice the size of the continental United States (about 3 million square
miles).
Experts fear that in the coming decades, half of the world's
remaining 6 billion acres of forests will be lost to agricultural expansion. If
forests continue to disappear at the current rate, as many as 20 percent of all
tropical forest species of plants and animals could become extinct in 30
years.
An August 2002 United Nations report predicted that agricultural
and urban expansion will threaten biodiversity on 72 percent of the global
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