Transcript Section 10 – Agriculture

Unit 1
Cell and Molecular
Biology
Section 10
Agriculture
Transgenic Plants
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A transgenic organism is an organism that is
carrying genetic material of another organism
in its genome.
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Producing a transgenic organism requires:
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A vector used to insert the required DNA into a plant
A way of ensuring the gene is carried in all cells
Vectors
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A vector is an agent used to transfer DNA
from one organism to another
Agrobacterium (tumerfaciens) is a commonly
used vector
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Agrobacterium is a soil bacteria
It contains a plasmid (known as Ti) which it can
insert into plant DNA causing a tumour (crown gall
disease)
Procedure for creating a transgenic
plant using a Ti-plasmid
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Ti disease gene is disabled
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Eg. By removing it with restriction enzymes
A target gene containing desired
characteristics is identified
A target gene is removed from source DNA
using a restriction enzyme
The plasmid is then cut using the same
restriction enzyme
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The foreign DNA (target gene) is then
added to the plasmid and sealed using
DNA ligase
The modified plasmid is returned to the
Agrobacterium
(Note the plasmid also has a method
for identification e.g antibiotic
resistance – later in the process this is
used to identify the cells that have the
plasmid)
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Plant cell protoplasts are prepared
The protoplasts are incubated with the
bacterium containing the modified plasmid
Grown in a selective medium that allows
only the growth of cells containing the
plasmid (and selected gene)
 E.g the medium may contain an antibiotic
Example 1 – insect resistance
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The bacteria Bacillus thuringiensis produces
proteins (known as BT toxins) that have been
used for insecticides
The toxin is isolated from the bacteria
genome and inserted into Ti plasmid of
agrobacterium
The resulting plant kills insects that eat it
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Potato, cotton and soybean are all plants
were this technique is used
Benefits
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Only insects eating the plant are killed
Reduces the use of pesticides
The entire plant has protection (not just the leaves
and stem, as would be the case if it was sprayed)
Example 2 – Tomato plants
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Tomato ripening is naturally accompanied by
softening due to an enzyme – PG
(polygalacturonase)
Fruit an usually picked while still green and
ripened artificially using ethene gas
By modifying the PG gene, fruit could be left
to ripen longer without softening
Fresher, riper tomatoes could be delivered to
supermarkets
Bovine Somatotrophin (BST)
production
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Bovine somatotrophin is a growth hormone
that can be used to increase growth (mainly
muscle and bone) and milk production in
cattle
The gene is isolated from cattle cells using
restriction enzymes
A restriction enzyme is also used to open a
plasmid from an E. coli bacteria
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The BST gene is inserted into the plasmid
using DNA ligase
The E.coli bacteria containing the plasmid are
then cultured
The gene is expressed (i.e. transcribed and
translated into protein form) during bacterial
growth
The protein is then purified and prepared for
administration to cattle
Use of BST
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BST is either administered by injection or the
protein is included in cattle feed
Results in a 10% increase in milk production
Disadvantages / concerns
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Can increase mastitis in cows
Lameness later in life – due to enlarged
udders
BST causes a lack of fat deposits (more of
the glucose etc.. is used) therefore
hypothermia can develop
BST found in milk – supposedly safe as it will
be broken down in our stomachs
Activities
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Monograph pg 90 – 94
DART pg 88 – 93
Scholar
Make flow diagrams / posters of the process of
 Creating transgenic plants
 BST production
Look at websites
 http://www.food.gov.uk/gmfoods/gmtt/gmplant
show
Moral and Ethical Issues related to
transgenic organisms
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Moral and Ethical codes attempt to establish
acceptable human behaviour for the benefit
of all society ‘DART’
Transgenic organisms
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What rights do they have?
Farmers
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What might there opinions towards transgenic be?
How might differing views on accompanying farms
be dealt with?
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Consumers
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The Environment
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What are the pros and cons?
What are the facts vs media hype?
Benefits vs problems
Biotechnology Industry
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Motives vs issues