1. GloFish, the first genetically modified animal to be sold as a pet
Genetically modified organism
2. A genetically modified organism (GMO) or
genetically engineered organism (GEO) is an
organism whose genetic material has been
altered using genetic engineering techniques.
These techniques, generally known as
recombinant DNA technology, use DNA molecules
from different sources, which are combined into
one molecule to create a new set of genes. This
DNA is then transferred into an organism, giving it
modified or novel genes. Transgenic organisms, a
subset of GMOs, are organisms which have
inserted DNA that originated in a different species.
3. Uses
GMOs are used in biological and medical research for the
production of pharmaceutical drugs, in experimental medicine
(e.g. gene therapy) and agriculture (e.g. golden rice). The
term "genetically modified organism" does not always imply,
but can include, targeted insertions of genes from one
species into another. For example a gene from a jellyfish,
encoding a fluorescent protein called GFP, can be physically
linked, and thus co-expressed, to mammalian genes to
identify the location of the protein encoded by the GFP-
tagged gene in the mammalian cell. Such methods are useful
tools for biologists in many areas of research, including those
who study the mechanisms of human diseases or
fundamental biological processes of eukaryotic or prokaryotic
cells.
4.
5. Different techniques are used for the
production of transgenic animals. The first
successful experiment of animal transgenesis
was achieved by using a retrovirus . This
technique is based on a phenomenon that
occurs in nature during viral infections. RNA of
the retrovirus enters the cell of the infected
animal: DNA is modified and integrated into
the host genome. This property makes a good
vector for retrovirus genetic material, although
this technique has some limits.
Transgenic animals
7. Other experiments have used embryonic stem
cells or germ cells, but the technique is currently
in use .
The main objectives of animal transgenesis are
the following:
• Production of biomedicine. Although the
production of biomolecules by bacteria or yeasts
is less expensive, these techniques have some
limitations due to metabolic differences of
bacterial cells from animal cells. For this reason it
was developed a great interest in the use of
techniques of transgenesis to produce large
quantities of molecules from animals used in
therapy and prevention such as drugs, antibodies
or vaccines.
8. The production of bio-molecules can occur
through different body fluids, whose exploitation
would be easier through milk, which is produced
in large quantities. Among the biomolecules
produced by transgenic animals, already at an
advanced stage of development, are polyclonal
antibodies and lactoferrin produced by bovine ,
antithrombin III factor produced by goats and
calcitonin produced by rabbits . Nevertheless
some undesirable effects have been reported
occasionally in animals used for these purposes,
such as lower production of milk or less duration
of lactation and infertility.
9. • Models for research on human disease.
Many diseases have a genetic origin, or have
predisposing factors in the genome. The study
of some diseases can be extremely easy using
the sperimental animal models that reproduce
some features of the human genome that are
at the basis of certain diseases. The use of
laboratory animals (especially mice and rats)
GM is already widespread in the study of a
number of diseases, mainly cancer .
10. • Xenotransplantation. One of the areas of
biotechnology research is the study of animals
can be donors of organs for
xenotransplantation. Xenotransplantation is
transplantation of organs from a nonhuman
species to humans, and may be a new frontier,
whereas the availability of organs for
allotransplantation (human to human) is
always less than the demand. The pig is
considered the most suitable species for this
purpose because it has some similarities in
terms of anatomy.
11. The biggest obstacle, however, is
immunological: the transplant recipient can
discards producing antibodies against the
transplanted organ. In this sense transgenic
approaches aim to inhibit the antibodies
reactions responsible for the rejection . Other
studies have focused on the transplantation of
transgenic cells or tissues, which could offer
interesting opportunities for the treatment of
various diseases such as Parkinson's disease
.
12. • Improvement of animal production. Among
the research on animal transgenesis, some are
intended to increase farm profitability by focusing
on genetic modification to improve the quality of
some products (eg milk, wool), to increase meat
production, fertility or the resistance diseases. An
experiment of 2003 showed that it is possible to
genetically engineer cows so they produce milk
with higher content of casein, a protein important
in the process of making cheese . Other
researchers have studied, in mice, the ability to
produce milk with reduced lactose content, which
could also be recruited by intolerant subjects
13. Fruit flies
In biological research, transgenic fruit flies
(Drosophila melanogaster) are model
organisms used to study the effects of genetic
changes on development. Fruit flies are often
preferred over other animals due to their short
life cycle, low maintenance requirements, and
relatively simple genome compared to many
vertebrates.
14. Cnidarians
Cnidarians such as Hydra and the sea
anemone Nematostella vectensis have
become attractive model organisms to study
the evolution of immunity and certain
developmental processes.
15.
16.
17. Gene therapy
Gene therapy, uses genetically modified viruses to deliver
genes that can cure disease into human cells. Although gene
therapy is still relatively new, it has had some successes. It
has been used to treat genetic disorders such as severe
combined immunodeficiency, and treatments are being
developed for a range of other currently incurable diseases,
such as cystic fibrosis, sickle cell anemia, and muscular
dystrophy. Current gene therapy technology only targets the
non-reproductive cells meaning that any changes introduced
by the treatment can not be transmitted to the next
generation. Gene therapy targeting the reproductive cells—
so-called "Germ line Gene Therapy"—is very controversial
and is unlikely to be developed in the near future.
21. il gene NptII codificante per l'enzima
neomicina fosfotrasferasi II che catalizza la
fosforilazione degli antibiotici neomicina e
kanamicina.
22. Transgenic plants have been engineered to
possess several desirable traits, including
resistance to pests, herbicides, or harsh
environmental conditions; improved product
shelf life, and increased nutritional value.
Since the first commercial cultivation of
genetically modified plants in 1996, they have
been modified to be tolerant to the herbicides
glufosinate and glyphosate, to be resistant to
virus damage as in Ringspot virus resistant
GM papaya, grown in Hawaii, and to produce
the Bt toxin, a potent insecticide.
23. Most of transgenic varieties grown today are
known as first generation transgenics, because
the transgenic trait provides benefits to farmers.
Plants of the second generation should directly
benefit the consumer with nutritional
enhancement, taste, texture, etc. Transgenic
plants of the second generation are being
developed by both public research institutions and
private companies. Currently there is no such
transgenic variety on the market. Genetically
modified sweet potatoes have been enhanced
with protein and other nutrients, while golden rice,
24. developed by the International Rice Research
Institute, has been discussed as a possible
cure for Vitamin A deficiency. In January 2008,
scientists altered a carrot so that it would
produce calcium and become a possible cure
for osteoporosis; however, people would need
to eat 1.5 kilograms of carrots per day to reach
the required amount of calcium.
25. The coexistence of GM plants with conventional
and organic crops has raised significant concern
in many European countries. Since there is
separate legislation for GM crops and a high
demand from consumers for the freedom of
choice between GM and non-GM foods,
measures are required to separate foods and feed
produced from GMO plants from conventional and
organic foods. European research programs such
as Co-Extra, Transcontainer, and SIGMEA are
investigating appropriate tools and rules. At the
field level, biological containment methods include
isolation distances and pollen barriers.
26. Foodchain
The safety of GMOs in the foodchain has been
questioned by some environmental groups, with
concerns such as the possibilities that GMOs
could introduce new allergens into foods, or
contribute to the spread of antibiotic resistance. All
studies published to date have shown no adverse
health effects resulting from humans eating
genetically modified foods, environmental groups
still discourage consumption in many countries,
claiming that GM foods are unnatural and
therefore unsafe. Such concerns have led to the
adoption of laws and regulations that require
safety testing of any new organism produced for
human consumption.
27. GMOs' proponents note that because of the
safety testing requirements imposed on GM
foods, the risk of introducing a plant variety
with a new allergene or toxin using genetic
modification is much smaller than using
traditional breeding processes. An example of
an allergenic plant created using traditional
breeding is the kiwi. One article calculated that
the marketing of GM salmon could reduce the
cost of salmon by half, thus increasing salmon
consumption and preventing 1,400 deaths
from heart attack a year in the United States.
28. Risks
• environmental risks related to changes in the
interaction between modified plants and biotic
environment, including persistence and
invasiveness, induction of resistance in insect
pests that are resistant plants, interactions with
non-target organisms (eg, effects on bees and
other insects no weeds, with consequences on
biodiversity);
• possible risks to human or animal health,
including toxicological effects caused by protein
synthesized by the introduced genes or toxicity of
constituents other than proteins, allergenicity,
changes in nutritional value and transfer of
resistance to antibiotics.
