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Unit 1 Cell and Molecular Biology

Unit 1 Cell and Molecular Biology. Section 10 Agriculture. 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

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Unit 1 Cell and Molecular Biology

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  1. Unit 1Cell and Molecular Biology Section 10 Agriculture

  2. 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

  3. 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)

  4. 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

  5. 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)

  6. 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

  7. 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

  8. 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)

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. Activities • 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/gmplantshow

  15. 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?

  16. Consumers • What are the pros and cons? • What are the facts vs media hype? • The Environment • Benefits vs problems • Biotechnology Industry • Motives vs issues

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