Notes 4.4
DP Biology
Gene transfer and GMO’s
Genetic engineering is a broad term for all the processes that result in the directed modification of an organism.
This includes plant an animal breeding and the deliberate gene transfer from one organism to another. There are
many applications of genetic engineering in industry, agriculture and medicine.
Scientists are now able to transfer genes into bacteria, plants, fungi and mammals. An organism that has received
genes from a different species is called a Transgenic Organism or Genetically Modified Organism (GMO)
The following discoveries have been key to the development of this technology:
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enzymes that can cut DNA from one chromosome and paste it into another
vectors that can carry the gene from one organism to another
culture techniques that allow large quantities of product to be produced.
In simple terms a gene transfer involves:
1. identification of genes important to humans,
removal of genes from the animal or plant that
normally shows this characteristic
2. genes are transferred to a vector often a virus.
3. virus used to transfer gene to desired organism.
4. organism reads the gene it has received
5. organism produces desired product
Lab Simulation of Transgenic Process
Transgenic animals can be produced by introducing a
desirable gene into the nucleus of a fertilized ovum
using a fine pipette. After the cell has divided to
produce a ball of cells it is implanted into a female
animal and grows in to a transgenic animal. This animal
will be able to make the protein coded for by the
desirable gene.
In some cases scientists transfer the desired gene into
the cells of the mammary glands. This way the protein
produced can be extracted from the milk, factor VIII
used to treat haemophilia is produced in this way.
In another process the desired gene is inserted into a
bacterium. The modified bacterium is then grown in
culture and is able to produce the protein coded for by
the gene ie the production of insulin.
The figure diagram on the left shows the production
of human insulin by bacteria.
Location of important genes
1. If part of the DNA sequence of the required gene is known a radioactive probe of complementary DNA can
be made. Thus the correct part of the genome can be identified and extracted.
2. If a cell produces large amounts of a particular protein then it will also have large amounts of the
corresponding RNA. This RNA can be ext acted and converted into DNA using the enzyme reverse
transcriptase.
3. If the base sequence is known it can now be artificially manufactured from DNA nucleotides
Restriction enzymes
Gene transfer was made possible by the discovery of restriction enzymes that are capable of cutting DNA at specific
sites. The enzymes are extracted from bacteria where there normal function is to protect the bacteria by cutting up
the DNA of any invading organisms , such as viruses or bacteria.
There are many different restriction enzymes
each capable of recognising a particular short
sequence of DNA and cutting the DNA at
these points. Most restriction enzymes
recognise sequences containing 4 to 8
nucleotides, because a sequence this short
will appear many times in a length of DNA,
many cuts are made and so many fragments
are obtained.
The most useful restriction enzymes cut the
DNA in a staggered way producing sticky ends
(free nucleotides). These short extensions can
form hydrogen bonds with complementary
sticky ends on another DNA molecule cut
with the same enzyme. These strands can
then be permanently joined using DNA ligase.
Thus DNA from two different sources are
joined permanently making recombinant DNA.
Plasmid
Plasmids and their uses in gene transfer
Plasmids are small loops of DNA found in bacteria. It is separate from the chromosomal DNA and is capable of self
replication, they provide the bacterium with extra information which can be key to the bacterium’s survival in times
of stress ie plasmids can make bacteria antibiotic resistant.
Plasmids used in gene transfer are called vectors. The gene
to be replicated is cut using a restriction enzyme
producing sticky ends, the same restriction enzyme is used
to cut open the plasmid. The DNA from the two sources
are then mixed, where firstly hydrogen bonds form
between the corresponding sticky ends and then
permanent joining is achieved through the addition of the
enzyme ligase.
Next the recombinant plasmids are inserted into bacteria
and the bacteria are allowed to multiply. The protein
produced by the gene may be harvested or the gene itself
may be harvested and inserted into another organism.
Genetic modification the ethics
Benefits
Genetically modified plants can reduce the need for
pesticides and fertilizers
Crops can be altered to cope with extreme conditions,
thus increasing area for cultivation and reducing
famine
Genetic engineering gives predictable results
Foods can be engineered to contain medicines such as
vaccines
Fruits can be manufactured with longer shelf lives
Problems
Plants engineered of r pesticide resistance could cross
breed with wild species creating super weeds
Engineered bacteria could escape from labs with
unknown consequences
Production of these organisms is expensive and
companies protect their investment by having patents
on the products. His makes the products very
expensive
Gene transfer in humans could lead to designer babies
Examples and Pictures:
Glo Fish:
First genetically modified animal to be sold as a pet.
Price:$5
Genetically Modified Corn
Genetically modified corn plant: pest-infected non-GM (left) and
pest-free GM plant (right) planted side-by-side in a field trial
 Research one genetically modified organism and write a brief report including: wha organisms
is, why it was created, how it was created.
Articles on the benefits:
 http://environment.newscientist.com/channel/earth/mg18925383.700-synthetic-wheat-offers-hope-tothe-world.html
 http://www.newscientist.com/channel/health/dn8120-mosquito-with-glowing-gonads-to-help-battlemalaria.html
Articles on the risks:
 http://www.newscientist.com/channel/health/mg18825274.100-gm-peas-cause-surprise-allergicreaction.html
 http://www.newscientist.com/channel/sex/mg18825283.900-concerns-over-ivf-contamination-risk.html
Other Information:
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http://www.newscientist.com/search.ns;jsessionid=DJIJLAOBPMCI?doSearch=true&query=genetic+modifica
tion
Gene Therapy
http://www.nettally.com/prusty/gene.htm
This is the transfer of healthy genes into a person’s cells. The new gene is able to substitute the mutant alleles that
causes the disease.
Cystic fibrosis is a good candidate for gene therapy because:
1. The healthy gene has been identified and is easily obtained
2. The diseased tissue in the lungs is easy to reach
3. The coat of the influenza virus can be used as a vector