Introducing New Genes Into Crops
- 1. Introducing new genes into crops Sometimes new genes can be introduced through diseases such as Agrobacterium tumefaciens The bacteriums plasmid T i is taken up by the host plant cells and they are replicated so they produce a hormone which stimulates the growth of the tumour. Techniques are available to remove the tumour producing genes with the normal genes This is done by using a vector (the vehicle used to carry the desired DNA) such as plasmid circular DNA The result is the production of undifferentiated tissue which can then be induced to transgenic plants which would contain the desirable genes
- 5. Producing chymosin Chymosin (rennin) is an enzyme involved in coagulation of casein (protein in milk). Before it would have been found in rennet which would have been extracted from the stomach of cows. Due to high demand other methods were sort after. 1) they tried to use bovine rennet, but it gave a low yield of cheese 2) they tried to use fungal enzymes which was good in comparison, but the disadvantage was that it has a long maturing stage, they overcame this problem by oxidising agents to destabilize the enzyme. It is also good for vegetarians. Chymosin is now produced by using genetically engineered yeast. This is done by obtaining the exact genes that make the enzymes and incorporate it into E.coli
- 7. Genetically modified organisms With the ‘cut’ and ‘paste’ techniques of DNA technology gives you the precise control of specific genes that are incorporated into the genome with success achieved in a shorter time period. Recombinant DNA technology has the potential to transfer genes from one organism into another. Sometimes genes are inserted into the plants so they can be resistant to weed killers, by breaking down the chemical into harmless components. Another techniques is by removing the plants cell wall and introduce the foreign DNA, this is done by treating it with cellulase, insert the genes through the plasma membrane before the cell wall is regenerated Some bacterium bacillus thuringiensis can produce a protein which is toxic to some insect larvae, but harmless to animals and humans. It is found on the plasmid of the bacterium, so it is introduced to the new protoplast (plant cells) and cultured to make crops that have a natural defence against pests
- 10. Genetic modification Use 2 different methods to the expression of the enzyme polygalacturonase (PG). This is done by using Agrobacterium as the vector, the ‘antisense’ (complimentary strand of nucleic acids) reversed form of the gene. PG gene is inserted into the tomato plant and inherited through the normal mendilian way