Worlds of David Darling > Children's
Encyclopedia of Science > Genetic Engineering > 4. Designer Genes
Redrawing the Blueprint of Life
a book in the Beyond 2000 series by David Darling
4. Designer Genes
One of the greatest scientific ventures of recent times has been the Human
Genome Project. Its goal, accomplished in 2003, was to map the position
of every one of the 100,000 or so genes strung out along the 23 pairs of
|A scientist in a French laboratory working
on mapping the human genome
The Human Genome Project marked a great leap forward in our efforts to learn
the causes of genetic disease. Because of it, scientists are now pinpointing
which genes are responsible for many of the genetic disorders that afflict
human beings. This information will be used by gene therapists to improve
greatly the understanding of diseases such as cystic fibrosis, hemophilia,
sickle-cell anemia (another blood disorder), and muscular dystrophy (a condition
in which a person's muscles gradually waste away). Improved knowledge of
the location of particular genes will help scientists develop better treatments
and eventually, perhaps, find permanent cures for these diseases.
Along with the benefits that gene therapy may bring, however, there are
dangers. In time, scientists may be able to make widespread changes to a
person's DNA. Genetic engineering may even progress to the point where it
becomes possible to design how a future human being will look.
Gene therapy and genetic engineering raise some important concerns. Few
people would doubt the value of gene therapy that can cure a serious disease
such as cystic fibrosis. But there is uncertainty over how much tampering
should be allowed with an individual's genetic makeup. Should gene therapy,
for instance, be used to correct minor genetic ailments like color blindness?
Should it be used to ensure that people do not grow up with crooked teeth
or flat feet?
If minor genetic conditions are eventually treated by gene therapy, people
may be tempted to go a step further. Some parents may wish to use genetic
engineering to select their baby's appearance.
Height, the color of eyes, hair, and skin, shoe size, muscle build, and
many other physical characteristics are determined, in part, by the coded
instructions in our genes. But should it be lawful to influence how a future
human being will look by altering a child's genes before birth?
Like many developments in science, genetic engineering could be used in
ways that are both good and bad for human beings. During the Second World
War, Adolf Hitler and other members of Germany's ruling Nazi party sought
to exterminate whole groups of people – such as Jews, homosexuals,
Gypsies, and disabled people – whom they considered to have inferior
genes. The Nazis' goal was to breed a new race of strong, white-skinned,
fair-haired people who would rule over everyone else. If, in the future,
other evil dictators like Hitler were to rise to power, they might try to
use genetic engineering for their own ends.
Mighty Mouse and Beyond
Not surprisingly, many doctors would like to see governments around the
world introduce strict rules to control the use of genetic engineering.
These rules would prevent altered genes from being passed on to future generations
– at least until the altered genes were proved to be safe. The regulations
would also ensure that gene therapy was used only to cure diseases and not
to help determine a person's appearance and other physical characteristics.
|The corn plants in this greenhouse have been
genetically engineered to resist attack by a pest called the European
The laws governing genetic engineering on human beings are likely to be
strict. However, scientists have already carried out wide-ranging experiments
on animals and plants. They have created TRANSGENC ANIMALS and plants by
taking genes from one organism and placing them in the DNA of a different
kind of creature.
In 1981, researchers took the gene for producing growth hormone in rats
and injected it into the fertilized eggs of mice. Growth hormone is a chemical
that controls how fast and how much an individual grows. The growth hormone
gene from the rats made the injected mice grow to be half as big again as
a normal mouse. However, the results of this type of experiment are hard
to predict. For example, when the human growth hormone gene was put into
the fertilized eggs of pigs, the pigs did not grow larger. Instead, they
produced leaner meat and were cross-eyed.
There is much debate about whether experiments should be carried out on
animals, particularly if the tests may cause any sort of suffering. Supporters
of genetic experiments on animals, however, argue that it is only through
research on other species that scientists can develop new forms of gene
therapy for human beings.
Animals have been genetically engineered to produce important, rare drugs
in their milk. These valuable medicines include insulin, which is needed
by people who suffer from diabetes, and antitrypsin, a chemical that can
help in the treatment of lung diseases.
|This transgenic ewe has been give the human
gene that causes the production of a protein called antitrypsin in
the sheep's milk. Her lamb (in the foreground) is also transgenic
for this protein.
To turn an animal into a kind of living drug factory, scientists extract,
from a human cell, the gene for making the required substance. Then this
gene is placed inside the nucleus of a fertilized egg of an animal, such
as a sheep. As the young sheep develops, each of its cells will include
a copy of the human gene. Finally, when the sheep has young of its own and
produces milk, its milk will contain small amounts of the substance for
which the human gene carries the code.
Research is now being done to improve the quantity of various types of drugs
produced in animals' milk. The yield of these drugs is expected to increase
gradually. By the beginning of the twenty-first century, large stocks of
animals such as sheep and cows may have been genetically engineered to produce
everything from blood-clotting substances for hemophilia sufferers to human
Through genetic engineering, entirely new kinds of life-forms are being
created. These include plants that make their own pesticides, bacteria that
boost the fertility of the soil in which they live, and other kinds of bacteria
that clean up pollution in oceans and rivers. By placing new genes into
existing life-forms, scientists can in effect design creatures to suit specific
|Researchers have genetically improved tomatoes
to reduce the production of a gas called ethene that causes tomatoes
to ripen. When the gene is inserted into the tomato plant, it slows
the ripening process. This allows the fruit to reach maturity on the
plant, providing customers with vine-ripened tomatoes year-round.
Much good may come from setting genetically engineered organisms free into
the environment. Already new kinds of GENETICALLY MODIFIED cereal crops,
fruits, and vegetables that can resist disease and pests have been developed.
Some plants are being designed that can produce their own insecticide. This
will allow farmers to use less chemical spray. Eventually crops may be tailored
to live in places where there is poor soil or very little rain.
But there are risks. Transgenic animals and plants are unknown in the natural
world. No one can be sure what effect these genetically altered life-forms
might have on other species. One danger is that a genetically engineered
organism might be safe in itself but its altered genes might be transferred
to other living things, which may be harmed. Another possibility is that
by making plants resistant to some kinds of germs, we will encourage the
evolution of other kinds of disease-causing germs.
In the United States, between 1974 and 1976, public concern was so great
that all research into genetic engineering was stopped. Then a set of guidelines
was introduced to control possible dangers. Most countries now have similar
rules. The first release of genetically engineered organisms, in the form
of pesticides, took place in the United States in 1985. Further releases
took placed under controlled conditions to ensure that introducing transgenic
animals and plants into the environment was done with the minimum of risk.
In 1994, the first genetically engineered produce went on sale in stores
around the United States. This included tomatoes in which the genes had
been altered so that the fruit would ripen without rotting. Meanwhile, environmentalists
are urging extreme caution before such "unnatural" living things are let
out of the laboratory.
|How to Sow Cress and Reap Plastic
In the future, farmers may grow plastics as a crop. Genetic engineers
in the United States have altered the genes in a plant known as thale
cress so that it produces a natural and totally biodegradable plastic
material called PHB.
The researchers took two genes from a kind of bacterium that makes
PHB naturally and stores it in the same way that human store fat.
Then they introduced these genes into the cells of a thale cress plant
so that it could make its own PHB. One problem is that the altered
cress tends to become sickly, perhaps because it uses up so much energy
in the production of the plastic. A way around this may be to put
the genes into other kinds of plants, such as sugar beets or potatoes,
that make great quantities of energy-storing substances like sugar
and starch. If further research is successful, the twenty-first century
could see farmers reaping harvests of plastic and other substances
alongside their fields of corn and cabbage.