Agriculture

Agriculture

Transgenic Plants

Production of Bovine Somatotrophin

Revision

How is genetic engineering oforganisms carried out (think back toSG and Higher)?

What is needed?

What is substances are producedthrough genetic engineering?

What else do we know?

Transgenic Plants

A transgenic organism is an organismthat is carrying genetic material ofanother organism in its genome.

Producing a transgenic organismrequires:

A vector used to insert the required DNAinto a plant

A way of ensuring the gene is carried in allcells

Vectors

A vector is an agent used to transferDNA from one organism to another

Agrobacterium (tumerfaciens) is acommonly used vector

Agrobacterium is a soil bacteria

It contains a plasmid (known as Ti)which it can insert into plant DNAcausing a tumour (crown gall disease)

Vectors cont…

Procedure for creating a transgenicplant using a Ti-plasmid

Ti disease gene is disabled

Eg. By removing it with restrictionenzymes

A target gene containing desiredcharacteristics is identified

A target gene is removed from sourceDNA using a restriction enzyme

The plasmid is then cut using thesame restriction enzyme

Procedure for creating a transgenicplant using Ti cont…

The foreign DNA (target gene) is thenadded to the plasmid and sealedusing DNA ligase

The modified plasmid is returned tothe Agrobacterium

(Note the plasmid also has a methodfor identification e.g antibioticresistance – later in the process thisis used to identify the cells that havethe plasmid)

Procedure for creating a transgenicplant using Ti cont…

Plant cell protoplasts are prepared

The protoplasts are incubated withthe bacterium containing the modifiedplasmid

Grown in a selective medium thatallows only the growth of cellscontaining the plasmid (and selectedgene)

E.g the medium may contain an antibiotic

Example 1 – insect resistance

The bacteria Bacillus thuringiensisproduces proteins (known as BTtoxins) that have been used forinsecticides

The toxin is isolated from the bacteriagenome and inserted into Ti plasmidof agrobacterium

The resulting plant kills insects thateat it

Example 1 – insect resistance

Potato, cotton and soybean are allplants were this technique is used

Benefits

Only insects eating the plant are killed

Reduces the use of pesticides

The entire plant has protection (not justthe leaves and stem, as would be thecase if it was sprayed)

Example 2 – Tomato plants

Tomato ripening is naturally accompaniedby softening due to an enzyme – PG(polygalacturonase)

Fruit an usually picked while still green andripened artificially using ethene gas

By modifying the PG gene, fruit could beleft to ripen longer without softening

Fresher, riper tomatoes could be deliveredto supermarkets

Bovine Somatotrophin (BST)production

Bovine somatotrophin is a growthhormone that can be used to increasegrowth (mainly muscle and bone) andmilk production in cattle

The gene is isolated from cattle cellsusing restriction enzymes

A restriction enzyme is also used toopen a plasmid from an E. colibacteria

Bovine Somatotrophin (BST)production

The BST gene is inserted into theplasmid using DNA ligase

The E.coli bacteria containing theplasmid are then cultured

The gene is expressed (i.e.transcribed and translated intoprotein form) during bacterial growth

The protein is then purified andprepared for administration to cattle

Use of BST

BST is either administered byinjection or the protein is included incattle feed

Results in a 10% increase in milkproduction

Disadvantages / concerns

Can increase mastitis in cows

Lameness later in life – due toenlarged udders

BST causes a lack of fat deposits(more of the glucose etc.. is used)therefore hypothermia can develop

BST found in milk – supposedly safeas it will be broken down in ourstomachs

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 Q8

Look at websites

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

Moral and Ethical Issues related totransgenic organisms

Moral and Ethical codes attempt toestablish acceptable human behaviour forthe benefit of all society ‘DART’

Transgenic organisms

What rights do they have?

Farmers

What might there opinions towards transgenicbe? How might differing views on accompanyingfarms be dealt with?

Moral and Ethical Issues related totransgenic 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 anduse of transgenic organisms

THE END OF UNIT ONE

•(Except for the NAB)