Agriculture

Transgenic PlantsProduction of Bovine Somatotrophin

Revision

How is genetic engineering of organisms carried out (think back to SG and Higher)?

What is needed? What is substances are produced

through genetic engineering? What else do we know?

Transgenic Plants

A transgenic organism is an organism that is carrying genetic material of another organism in its genome.

Producing a transgenic organism requires:

A vector used to insert the required DNA into a plant

A way of ensuring the gene is carried in all cells

Vectors

A vector is an agent used to transfer DNA from one organism to another

Agrobacterium (tumerfaciens) is a commonly used vector 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)

Vectors cont…

Procedure for creating a transgenic plant using a Ti-plasmid

Ti disease gene is disabled 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

Procedure for creating a transgenic plant using Ti cont…

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)

Procedure for creating a transgenic plant using Ti cont…

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 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

Example 1 – insect resistance

Potato, cotton and soybean are all plants were this technique is used

Benefits 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 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

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

Bovine Somatotrophin (BST) production

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

BST is either administered by injection or the protein is included in cattle feed

Results in a 10% increase in milk production

Disadvantages / concerns 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

Learning Activities Monograph pg 90 – 94 DART pg 88 – 93 Scholar Genetically Modified Plants worksheet Make flow diagrams / posters of the process of

Creating transgenic plants BST production

Assignment Questions – 2001 Q12, 2005 Section B Q 8 Look at websites

http://www.food.gov.uk/gmfoods/gmtt/gmplantshow

Moral and Ethical Issues related to transgenic organisms

Moral and Ethical codes attempt to establish acceptable human behaviour for the benefit of all society ‘DART’

Transgenic organisms What rights do they have?

Farmers What might there opinions towards transgenic

be? How might differing views on accompanying farms be dealt with?

Moral and Ethical Issues related to transgenic organisms

Consumers What are the pros and cons? What are the facts vs media hype?

The Environment Benefits vs problems

Biotechnology Industry Motives vs issues

Formal Debate

This house supports the creation and use of transgenic organisms

THE END OF UNIT ONE

• (Except for the NAB)