Реферат: Genetic Engineering

Реферат: Genetic Engineering

All that we are is the result of what we have thought

Buddha

For what shall it profit a man, if he shall gain

the whole world and lose his own soul?

The Bible

Introduction

While plant biotechnology has been used for centuries to enhance plants,

microorganisms and animals for food, only recently has it allowed for the

transfer of genes from one organism to another. Yet there is now a widespread

controversy over the harmful and beneficial effects of genetic engineering to

which, at this time, there seems to be no concrete solution. The ideas below

are expected to bring in a bit of clearance into the topic. Here I’m going to

reveal some facts concerning genetic engineering, specially the technology,

its weak and strong points (if any). Probably the information brought is a

bit too prejudiced, for I’m certainly not in favor of making jokes with

nature, but I really tried to find some good things about GE.

What is genetic engineering?

Genetic engineering is a laboratory technique used by scientists to change

the DNA of living organisms.

DNA is the blueprint for the individuality of an organism. The organism

relies upon the information stored in its DNA for the management of every

biochemical process. The life, growth and unique features of the organism

depend on its DNA. The segments of DNA which have been associated with

specific features or functions of an organism are called genes.

Molecular biologists have discovered many enzymes which change the structure

of DNA in living organisms. Some of these enzymes can cut and join strands of

DNA. Using such enzymes, scientists learned to cut specific genes from DNA

and to build customized DNA using these genes. They also learned about

vectors, strands of DNA such as viruses, which can infect a cell and insert

themselves into its DNA.

With this knowledge, scientists started to build vectors which incorporated

genes of their choosing and used the new vectors to insert these genes into

the DNA of living organisms. Genetic engineers believe they can improve the

foods we eat by doing this. For example, tomatoes are sensitive to frost.

This shortens their growing season. Fish, on the other hand, survive in very

cold water. Scientists identified a particular gene which enables a flounder

to resist cold and used the technology of genetic engineering to insert this

'anti-freeze' gene into a tomato. This makes it possible to extend the

growing season of the tomato.

At first glance, this might look exciting to some people. Deeper

consideration reveals serious dangers.

Techniques

There are 4 types of genetic engineering which consist of recombinant

engineering, microinjection, electro and chemical poration, and also

bioballistics.

r-DNA technology

The first of the 4, recombinant engineering, is also known as r-DNA

technology. This technology relies on biological vectors such as plasmids and

viruses to carry foreign genes into cells. The plasmids are small circular

pieces of genetic material found in bacteria that can cross species

boundaries. These circular pieces can be broken, which results with an

addition of a new genetic material to the broken plasmids. The plasmids, now

joined with the new genetic material, can move across microbial cell

boundaries and place the new genetic material next to the bacterium's own

genes. After this takes place, the bacteria will then take up the gene and

will begin to produce the protein for which the gene codes. In this

technique, the viruses also act as vectors. They are infectious particles

that contain genetic material to which a new gene can be added. Viruses carry

the new gene into a recipient cell driving the process of infecting that

cell. However, the viruses can be disabled so that when it carries a new gene

into a cell, it cannot make the cell reproduce or make copies of the virus.

Microinjection

The next type of genetic engineering is referred to as microinjection. This

technique does not rely on biological vectors, as does r-DNA. It is somewhat

of a simple process. It is the injecting of genetic material containing the

new gene into the recipient cell. Where the cell is large enough, injection

can be done with a fine-tipped glass needle. The injected genes find the host

cell genes and incorporate themselves among them.

Electro and chemical poration

This technique is a direct gene transfer involving creating pores or holes in

the cell membrane to allow entry of the new genes. If it is done by bathing

cells in solutions of special chemicals, then it is referred to as chemical

poration. However, if it goes through subjecting cells to a weak electric

current, it is called electroporation.

Bio ballistics

This last technique is a projectile method using metal slivers to deliver the

genetic material to the interior of the cell. These small slivers, which must

be smaller than the diameter of the target cell, are coated with genetic

material. The coated slivers are propelled into the cells using a shotgun.

After this has been done, a perforated metal plate stops the shell cartridge

but still allows the slivers to pass through and into living cells on the

other side. Once inside, the genetic material is transported to the nucleus

where it is incorporated among host cells.

The history of GE

The concept was first introduced by an Australian monk named Gregor Mendel in

the 19th century. His many experiments cemented a foundation for future

scientists and for the founding concepts in the study of genetics.

Throughout Mendel's life, he was a victim of criticism and ridicule by his

fellow monks for his "foolish" experiments. It took 35 years until he was

recognized for his experiments and known for the selective breeding process.

Mendel's discoveries made scientists wonder how information was transferred

from parent to offspring and whether the information could be captured and/or

manipulated.

James D. Watson and Francis H. C. Crick were curious scientists who later

became known as the founding fathers of genetic engineering.

Watson and Crick wanted to determine how genetic blueprints are determined

and they also proposed that DNA structures are genetic messengers or that

chemical compounds of proteins and amino acids all come together as a way to

rule out characteristics and traits. These 2 scientists produced a code of

DNA and thus answered the question of how characteristics are determined.

They also established that DNA are the building blocks of all organisms.

Selective breeding and genetic engineering

Selective breeding and genetic engineering are "both used for the improvement

of human society." However, selective breeding is a much longer and more

expensive process than genetic engineering. It takes genetic engineering only

one generation of offspring to see and study improvement as opposed to

selective breeding where many generations are necessary. Therefore, it costs

more to observe many generations.

Selective breeding is known as the natural way to engineer genes while

genetic engineering is more advanced, technical, scientific, complex and is

inevitable in out future.

What are the dangers?

Many previous technologies have proved to have adverse effects unexpected by

their developers. DDT, for example, turned out to accumulate in fish and thin

the shells of fish-eating birds like eagles and ospreys. And

chlorofluorocarbons turned out to float into the upper atmosphere and destroy

ozone, a chemical that shields the earth from dangerous radiation. What

harmful effects might turn out to be associated with the use or release of

genetically engineered organisms?

This is not an easy question. Being able to answer it depends on

understanding complex biological and ecological systems. So far, scientists

know of no generic harms associated with genetically engineered organisms.

For example, it is not true that all genetically engineered foods are toxic

or that all released engineered organisms are likely to proliferate in the

environment. But specific engineered organisms may be harmful by virtue of

the novel gene combinations they possess. This means that the risks of

genetically engineered organisms must be assessed case by case and that these

risks can differ greatly from one gene-organism combination to another.

So far, scientists have identified a number of ways in which genetically

engineered organisms could potentially adversely impact both human health and

the environment. Once the potential harms are identified, the question

becomes how likely are they to occur. The answer to this question falls into

the arena of risk assessment.

In addition to posing risks of harm that we can envision and attempt to

assess, genetic engineering may also pose risks that we simply do not know

enough to identify. The recognition of this possibility does not by itself

justify stopping the technology, but does put a substantial burden on those

who wish to go forward to demonstrate benefits.

Fundamental Weaknesses of the Concept

Imprecise Technology—A genetic engineer moves genes from one organism to

another. A gene can be cut precisely from the DNA of an organism, but the

insertion into the DNA of the target organism is basically random. As a

consequence, there is a risk that it may disrupt the functioning of other genes

essential to the life of that organism. (Bergelson 1998)

Side Effects—Genetic engineering is like performing heart surgery with a

shovel. Scientists do not yet understand living systems completely enough to

perform DNA surgery without creating mutations which could be harmful to the

environment and our health. They are experimenting with very delicate, yet

powerful forces of nature, without full knowledge of the repercussions.

(Washington Times 1997)

Widespread Crop Failure—Genetic engineers intend to profit by patenting

genetically engineered seeds. This means that, when a farmer plants genetically

engineered seeds, all the seeds have identical genetic structure. As a result,

if a fungus, a virus, or a pest develops which can attack this particular crop,

there could be widespread crop failure. (Robinson 1996)

Threatens Our Entire Food Supply—Insects, birds, and wind can carry

genetically altered seeds into neighboring fields and beyond. Pollen from

transgenic plants can cross-pollinate with genetically natural crops and wild

relatives. All crops, organic and non-organic, are vulnerable to contamination

from cross-pollinatation. (Emberlin 1999)

Health Hazards

Here are the some examples of the potential adverse effects of genetically

engineered organisms may have on human health. Most of these examples are

associated with the growth and consumption of genetically engineered crops.

Different risks would be associated with genetically engineered animals and,

like the risks associated with plants, would depend largely on the new traits

introduced into the organism.

New Allergens in the Food Supply

Transgenic crops could bring new allergens into foods that sensitive

individuals would not know to avoid. An example is transferring the gene for

one of the many allergenic proteins found in milk into vegetables like

carrots. Mothers who know to avoid giving their sensitive children milk would

not know to avoid giving them transgenic carrots containing milk proteins.

The problem is unique to genetic engineering because it alone can transfer

proteins across species boundaries into completely unrelated organisms.

Genetic engineering routinely moves proteins into the food supply from

organisms that have never been consumed as foods. Some of those proteins

could be food allergens, since virtually all known food allergens are

proteins. Recent research substantiates concerns about genetic engineering

rendering previously safe foods allergenic. A study by scientists at the

University of Nebraska shows that soybeans genetically engineered to contain

Brazil-nut proteins cause reactions in individuals allergic to Brazil nuts.

Scientists have limited ability to predict whether a particular protein will

be a food allergen, if consumed by humans. The only sure way to determine

whether protein will be an allergen is through experience. Thus importing

proteins, particularly from nonfood sources, is a gamble with respect to

their allergenicity.

Antibiotic Resistance

Genetic engineering often uses genes for antibiotic resistance as "selectable

markers." Early in the engineering process, these markers help select cells

that have taken up foreign genes. Although they have no further use, the

genes continue to be expressed in plant tissues. Most genetically engineered

plant foods carry fully functioning antibiotic-resistance genes.

The presence of antibiotic-resistance genes in foods could have two harmful

effects. First, eating these foods could reduce the effectiveness of

antibiotics to fight disease when these antibiotics are taken with meals.

Antibiotic-resistance genes produce enzymes that can degrade antibiotics. If

a tomato with an antibiotic-resistance gene is eaten at the same time as an

antibiotic, it could destroy the antibiotic in the stomach.

Second, the resistance genes could be transferred to human or animal

pathogens, making them impervious to antibiotics. If transfer were to occur,

it could aggravate the already serious health problem of antibiotic-resistant

disease organisms. Although unmediated transfers of genetic material from

plants to bacteria are highly unlikely, any possibility that they may occur

requires careful scrutiny in light of the seriousness of antibiotic

resistance.

In addition, the widespread presence of antibiotic-resistance genes in

engineered food suggests that as the number of genetically engineered

products grows, the effects of antibiotic resistance should be analyzed

cumulatively across the food supply.

Production of New Toxins

Many organisms have the ability to produce toxic substances. For plants, such

substances help to defend stationary organisms from the many predators in

their environment. In some cases, plants contain inactive pathways leading to

toxic substances. Addition of new genetic material through genetic

engineering could reactivate these inactive pathways or otherwise increase

the levels of toxic substances within the plants. This could happen, for

example, if the on/off signals associated with the introduced gene were

located on the genome in places where they could turn on the previously

inactive genes.

Concentration of Toxic Metals

Some of the new genes being added to crops can remove heavy metals like

mercury from the soil and concentrate them in the plant tissue. The purpose

of creating such crops is to make possible the use of municipal sludge as

fertilizer. Sludge contains useful plant nutrients, but often cannot be used

as fertilizer because it is contaminated with toxic heavy metals. The idea is

to engineer plants to remove and sequester those metals in inedible parts of

plants. In a tomato, for example, the metals would be sequestered in the

roots; in potatoes in the leaves. Turning on the genes in only some parts of

the plants requires the use of genetic on/off switches that turn on only in

specific tissues, like leaves.

Such products pose risks of contaminating foods with high levels of toxic

metals if the on/off switches are not completely turned off in edible

tissues. There are also environmental risks associated with the handling and

disposal of the metal-contaminated parts of plants after harvesting.

Enhancement of the Environment for Toxic Fungi

Although for the most part health risks are the result of the genetic

material newly added to organisms, it is also possible for the removal of

genes and gene products to cause problems. For example, genetic engineering

might be used to produce decaffeinated coffee beans by deleting or turning

off genes associated with caffeine production. But caffeine helps protect

coffee beans against fungi. Beans that are unable to produce caffeine might

be coated with fungi, which can produce toxins. Fungal toxins, such as

aflatoxin, are potent human toxins that can remain active through processes

of food preparation.

No Long-Term Safety Testing

Genetic engineering uses material from organisms that have never been part of

the human food supply to change the fundamental nature of the food we eat.

Without long-term testing no one knows if these foods are safe.

Decreased Nutritional Value

Transgenic foods may mislead consumers with counterfeit freshness. A

luscious-looking, bright red genetically engineered tomato could be several

weeks old and of little nutritional worth.

Problems Cannot Be Traced

Without labels, our public health agencies are powerless to trace problems of

any kind back to their source. The potential for tragedy is staggering.

Side Effects can Kill

37 people died, 1500 were partially paralyzed, and 5000 more were temporarily

disabled by a syndrome that was finally linked to tryptophan made by

genetically-engineered bacteria.

Unknown Harms

As with any new technology, the full set of risks associated with genetic

engineering have almost certainly not been identified. The ability to imagine

what might go wrong with a technology is limited by the currently incomplete

understanding of physiology, genetics, and nutrition.

Potential Environmental Harms

Increased Weediness

One way of thinking generally about the environmental harm that genetically

engineered plants might do is to consider that they might become weeds. Here,

weeds means all plants in places where humans do not want them. The term

covers everything from Johnson grass choking crops in fields to kudzu

blanketing trees to melaleuca trees invading the Everglades. In each case,

the plants are growing unaided by humans in places where they are having

unwanted effects. In agriculture, weeds can severely inhibit crop yield. In

unmanaged environments, like the Everglades, invading trees can displace

natural flora and upset whole ecosystems.

Some weeds result from the accidental introduction of alien plants, but many

were the result of purposeful introductions for agricultural and

horticultural purposes. Some of the plants intentionally introduced into the

United States that have become serious weeds are Johnson grass, multiflora

rose, and kudzu. A new combination of traits produced as a result of genetic

engineering might enable crops to thrive unaided in the environment in

circumstances where they would then be considered new or worse weeds. One

example would be a rice plant engineered to be salt-tolerant that escaped

cultivation and invaded nearby marine estuaries.

Gene Transfer to Wild or Weedy Relatives

Novel genes placed in crops will not necessarily stay in agricultural fields.

If relatives of the altered crops are growing near the field, the new gene

can easily move via pollen into those plants. The new traits might confer on

wild or weedy relatives of crop plants the ability to thrive in unwanted

places, making them weeds as defined above. For example, a gene changing the

oil composition of a crop might move into nearby weedy relatives in which the

new oil composition would enable the seeds to survive the winter.

Overwintering might allow the plant to become a weed or might intensify weedy

properties it already possesses.

Change in Herbicide Use Patterns

Crops genetically engineered to be resistant to chemical herbicides are

tightly linked to the use of particular chemical pesticides. Adoption of

these crops could therefore lead to changes in the mix of chemical herbicides

used across the country. To the extent that chemical herbicides differ in

their environmental toxicity, these changing patterns could result in greater

levels of environmental harm overall. In addition, widespread use of

herbicide-tolerant crops could lead to the rapid evolution of resistance to

herbicides in weeds, either as a result of increased exposure to the

herbicide or as a result of the transfer of the herbicide trait to weedy

relatives of crops. Again, since herbicides differ in their environmental

harm, loss of some herbicides may be detrimental to the environment overall.

Squandering of Valuable Pest Susceptibility Genes

Many insects contain genes that render them susceptible to pesticides. Often

these susceptibility genes predominate in natural populations of insects.

These genes are a valuable natural resource because they allow pesticides to

remain as effective pest-control tools. The more benign the pesticide, the

more valuable the genes that make pests susceptible to it.

Certain genetically engineered crops threaten the continued susceptibility of

pests to one of nature's most valuable pesticides: the Bacillus thuringiensis

or Bt toxin. These "Bt crops" are genetically engineered to contain a gene

for the Bt toxin. Because the crops produce the toxin in most plant tissues

throughout the life cycle of the plant, pests are constantly exposed to it.

This continuous exposure selects for the rare resistance genes in the pest

population and in time will render the Bt pesticide useless, unless specific

measures are instituted to avoid the development of such resistance.

Poisoned Wildlife

Addition of foreign genes to plants could also have serious consequences for

wildlife in a number of circumstances. For example, engineering crop plants,

such as tobacco or rice, to produce plastics or pharmaceuticals could

endanger mice or deer who consume crop debris left in the fields after

harvesting. Fish that have been engineered to contain metal-sequestering

proteins (such fish have been suggested as living pollution clean-up devices)

could be harmful if consumed by other fish or raccoons.

Creation of New or Worse Viruses

One of the most common applications of genetic engineering is the production

of virus-tolerant crops. Such crops are produced by engineering components of

viruses into the plant genomes. For reasons not well understood, plants

producing viral components on their own are resistant to subsequent infection

by those viruses. Such plants, however, pose other risks of creating new or

worse viruses through two mechanisms: recombination and transcapsidation.

Recombination can occur between the plant-produced viral genes and closely

related genes of incoming viruses. Such recombination may produce viruses

that can infect a wider range of hosts or that may be more virulent than the

parent viruses.

Transcapsidation involves the encapsulation of the genetic material of one

virus by the plant-produced viral proteins. Such hybrid viruses could

transfer viral genetic material to a new host plant that it could not

otherwise infect. Except in rare circumstances, this would be a one-time-only

effect, because the viral genetic material carries no genes for the foreign

proteins within which it was encapsulated and would not be able to produce a

second generation of hybrid viruses.

Gene Pollution Cannot Be Cleaned Up

Once genetically engineered organisms, bacteria and viruses are released into

the environment it is impossible to contain or recall them.

Unlike chemical or nuclear contamination, negative effects are irreversible.

DNA is actually not well understood.

Yet the biotech companies have already planted millions of acres with

genetically engineered crops, and they intend to engineer every crop in the

world.

The concerns above arise from an appreciation of the fundamental role DNA

plays in life, the gaps in our understanding of it, and the vast scale of

application of the little we do know. Even the scientists in the Food and

Drug administration have expressed concerns.

Unknown Harms

As with human health risks, it is unlikely that all potential harms to the

environment have been identified. Each of the potential harms above is an

answer to the question, "Well, what might go wrong?" The answer to that

question depends on how well scientists understand the organism and the

environment into which it is released. At this point, biology and ecology are

too poorly understood to be certain that question has been answered

comprehensively.

Any pros?

Certainly, there should be some. Still, most of them are connected with

commercial gains for genetic engineering companies. A popular claim, that

farmers will benefit, is simply not true. It is just the same thing with

consumers. No one is going to feed the poorest with GE products for the famine

in many underdeveloped countries is simply the matter of inability to buy

food, not lack of it. So today, at the present stage of development, we

hardly need GE expanding on food products, needless to say about animal and

human cloning. Incidentally, some daydreaming proponents of GE really believe

that mankind will not be able to survive without it. According to them, we will

certainly have to genetically upgrade ourselves in response to governmental

activities. The humans will be able to hibernate – just like some animals – to

cover long distances without aging, and, probably, will become immortal.

Still, what about the present need of GE? Where can GE particularly be used

now without a threat to the humans and the environment?

So, scientists say that genetic engineering can make it possible to battle

disease (cancer, in particular), disfigurement, and other maladies through a

series of medical breakthroughs that will be beneficial to the human race.

Moreover, cloning will be able to end the extinction of many endangered

species. The main question is whether we can trust genetic engineering. The

fact is that even genetically changed corn is already killing species.

The recent research showed that pollen from genetically engineered corn

plants is toxic to monarch butterflies. Corn plants produce huge quantities

of pollen, which dusts the leaves of plants growing near corn fields. Close

to half the monarch caterpillars that fed on milkweed leaves dusted with Bt

corn pollen died. Surviving caterpillars were about half the size of

caterpillars that fed on leaves dusted with pollen from non-engineered corn.

Something is wrong with the engineered products – they are different, so we

cannot be sure about the effect they will bring about.

So, is the technology trustworthy? I suppose not.

Conclusion

So, do we need it? There are far too many disadvantages of GE and far too

many unpredictable things may happen. The humans are amateurs in this area,

in fact, they are just like a monkey taught to press PC buttons. We have

almost no experience, the technology has not yet evolved enough. I believe,

we should wait, otherwise we may give birth to a trouble, which would be

impossible to resolve.

References

1. David Heaf ‘Pros and Cons of Genetic Engineering’, 2000, ifgene;

2. Ricarda Steinbrecher, 'From Green to Gene Revolution', The

Ecologist,

Vol 26 No 6;

3. ‘Genetic Engineering Kills Monarch Butterflies’, Nature Magazine, May

19,1999;

4. ‘Who's Afraid of Genetic Engineering?’ The New York Times August 26,

1998;

5. Sara Chamberlain ‘Techno-foods’, August 19, 1999, The New

Internationalist;

6. W French Anderson, 'Gene Therapy' in Scientific American, September

1995;

7. Nature Biotechnology Vol 14 May 1996;

8. Andrew Kimbrell 'Breaking the Law of Life' in Resurgence May/June

1997 Issue 182;

9. Jim Hightower ‘What’s for dinner?’, May 29, 2000.

Contents

Introduction_________________________________________________________ 1

What is genetic engineering?___________________________________________ 1

Techniques________________________________________________________ 1

The history of GE_____________________________________________________ 2

Selective breeding and genetic engineering______________________________ 3

What are the dangers?_________________________________________________ 3

Fundamental Weaknesses of the Concept________________________________ 3

Health Hazards_____________________________________________________ 4

Potential Environmental Harms________________________________________ 6

Any pros?___________________________________________________________ 8

Conclusion__________________________________________________________ 9

References__________________________________________________________ 10