How
to produce an insect resistant tomato plant?
What are genes, and where are they found?
There are genes in everything that lives, or has lived.
There are genes in people, flies, ham, tomatoes, bacteria
etc. A 200g steak contains 750,000,000,000,000 genes.
A gene is a code that governs how we appear and what characteristics
we have. There are, for example, genes which decide whether
we have blue or brown eyes. We receive half of our genes from
our mother, the other half from our father.
Plants have genes too. Genes decide the colour of flowers,
and how tall a plant can grow. Like people, the characteristics
of a plant will be transferred to its children- the plant
seeds, which grow into new plants.
What is genetic modification?
Genetic modification changes the genes and thereby the
characteristics of the subject. You can, for example, genetically
modify strawberries so that they stay fresh for longer, and
rice can be genetically modified so that it has a higher vitamin
content.
When a scientist genetically modifies a plant, they insert
a foreign gene in the plant's own genes. This might be a gene
from a bacterium resistant to pesticide, for example. The
result is that the plant receives the characteristics held
within the genetic code. Consequently, the genetically modified
plant also becomes able to withstand pesticides.
With genetic modification it is possible to transfer genes
from one species to another. This is because all genes, be
they human, plant, animal or bacterial are created from the
same material. Genetic scientists therefore have a huge amount
of genetic characteristics to choose from.
How does a genetic scientist work?
Genetic modification of plants occurs in several stages:
| 1. |
The scientist finds and isolates the gene
with the desired genetic characteristics. This process
is called mapping. |
| 2. |
The scientist makes several copies of the
isolated gene. The copying process is called PCR. |
| 3. |
The scientist transfers the desired genes
to the plant's own genes (using a piece of plant tissue).
When the scientist wishes to insert the desired genes
into the plant - there are 3 options. He or she can use
a 'gene canon', a soil bacteria or a material called protoplast.
The methods of gene insertion are called 'transformation'. |
| 4. |
The scientist creates a new plant from
the genetically modified plant tissue. |
| 5. |
The scientist checks that the inserted
genes function as expected. |
| 6. |
The scientist also checks that the inserted
gene appears in the plant's progeny, that is - in the
seeds. |
How do we know if the genetic modification has succeeded?
Only rarely can one see whether a plant or animal has
been genetically modified, with the naked eye. Scientists
have therefore developed some techniques to assist them.
For example - a special colour test can identify whether
a plant is genetically modified. At the time when the plant
is genetically modified, the scientist inserts an extra marker
gene into the plant. The marker gene can have different characteristics,
for example, it can make the plant change colour when exposed
to a chemical test.
In this way, scientists can identify whether the plant has
been genetically modified or not by performing a chemical
test and noting the colour of the plant.
What is the difference between genetic modification and
traditional processing?
Long before the discovery of genetic modification, farmers
have improved their crops by what we today call "traditional
processing".
Processing is when one crosses the best, largest, most attractive
or best tasting samples of a certain species with each other
in order to get a plant or animal, that is even better, larger,
more attractive or better tasting.
In traditional processing genes are transferred from one
plant to another. This is also the case with genetic modification
- however the way in which it is done is very different.
Genetic modification is a more precise technique, where one
can be exact in transferring the desired characteristics.
In traditional processing one cannot avoid the possibility
that other characteristics may also be transferred.
In traditional processing, characteristics can only be exchanged
between species which are the same or very similar. In genetic
modification, characteristics can be transferred from one
species to a quite different one, even between plants and
animals.
Genetic modification is less time-consuming than traditional
processing.
In what other ways can genes be altered?
Not only genetic modification can be used to change animal
and plant genes.
Spontaneous changes, radiation, chemicals and traditional
processing can also alter the characteristics of a plant or
animal.
Spontaneous alteration of genes takes place naturally and
sometimes with no effect. A spontaneous alteration can lead
to the development of both positive and negative characteristics.
The method is not particularly good if the intention is to
create specific changes.
Radiation and chemicals can be used in order to effect gene
alteration. Both elements are sometimes used in plant processing.
In traditional processing closely related plant or animals
are crossed. It might be maize and navew or a horse and a
donkey. In this way different combinations of genes occur
in the progeny. Those with desirable characteristics are selected
over several generations. The crops and livestock we see today
are a result of traditional processing.
Can everything be genetically modified?
Yes. In principle anything that lives can be genetically
modified - animals, people, plants and bacteria.
You can in other words transfer characteristics from a fish
to a strawberry. But the less alike the species are, the more
difficult it is. It is easiest to genetically modify related
species.
Not all characteristics can be transferred. Some characteristics
occur only by interaction between many genes. Only rarely
do scientists have a good enough view of this interaction
to be able to recreate it.
At the moment, scientists are working intensely on mapping
genes in humans and pigs. Perhaps it will give them sufficient
knowledge and vision so that in the future they can create
even more complicated genetic modifications than today.
What
is inheritance?
What is a gene?
What
is a chromosome?
What is DNA?
What is
a protein?
What is
mitosis/meiosis?
Genetic testing for
disease
How to clone a human embryo to cure disease?
How to get stem cells from an embryo?
PCR
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