A GM future
- Genetically modified maize, soya and cotton are widely grown in both developed and developing countries.
- Many of these have a gene that makes them resistant to an herbicide. This means crops are not damaged by the chemical but the weeds growing with them are killed.
- In 2008, a new purple GM variety of tomato was developed and it was claimed that they help to treat cancer.
- It contains snapdragon genes that produce extra pigments called flavonoids. Tests have shown mice with cancer live longer, but this GM tomato may be too expensive for people in developing countries to grow or buy.
- GM crop seeds produced in developed countries are more expensive than normal seeds. Indian farmers borrowing money to buy GM seeds with the belief they would get a better crop yield than normal plants. However many found that the GM plants produced less food because they were not adapted to the Indian soil and climate.
Making GM plants
- A transgenic organism contains genes transferred from another organism. Transgenic plants are often produced using a vector, such as the bacteria Agrobacterium tumefaciens.
Genetically modifying plants with Agrobacterium tumefaciens
- A plant which is already herbicide resistant is found and the gene responsible for the resistance is located.
- The gene for herbicide-resistance is cut out from one of plant’s cells.
- Agrobacterium tumefaciens contain plasmids. These are removed from the bacteria, ‘cut open’ and inserted into the herbicide-resistance gene.
- The genetically modified bacteria then infect the target plant. A crown gall on the plant will occur which is swelling of the plant.
- This is when the bacteria have inserted their genes into the plant’s DNA.
- Tissue from this crown gall is grown in a medium. The cells contain the herbicide. Those that grown must contain the herbicide-resistant gene.
Advantages and Disadvantages of Bt crops
- Bacillus Thuringiensis is a bacterium that is normally found in soil. It produces a Bt toxin, which when eaten by insects is poisonous.
- Plants with the gene to produce Bt toxin can kill insects as when they eat the plant cells, the cells release the toxin. Less insecticide has to be sprayed onto the crop as a result, reducing the damage to the environment. Higher yields are thus produced, as less of the crop is lost to the pests.
- However, it possible that the toxin can kill other harmless insects such as butterflies and bees. The toxin can also spread if the pollen of the transgenic plant is transferred to a wild plant species.
Another problem is that many insect populations have evolved resistance to the Bt toxin, so they can live and breed on the Bt plants.