07-28-2010, 09:35 PM
(This post was last modified: 07-28-2010, 11:43 PM by joshuajoby.)
Genetically modified crops (GM Crops), the most talked about topic around the world has its own advantages and disadvantages. What are GM crops? Crops that have been modified from its natural genetic make up so as to yield better (?) characteristics. Genetic modifications are generally done in the gene expression level; either introducing desired gene to be expressed, or silencing the characters which it already possess. Though it possesses so many advantages, the degree of acceptance varies from country to country out of concern. There are number of GM crops out in production today. Genetically modifying crops have an enormous impact on improving the quality of the crops. Disease resistant plants are one of the major highlights of GM crops. The complex mechanism of host-pathogen interactions are unclear, so isolating a single gene responsible seems to be a tedious task though efforts have made.
Disease resistant plants- Resistance towards many viruses as well as fungus could be achieved. An expression vector with CaMV (Cauliflower mosaic virus) 35S promoter, cDNA of TMV(Tobacco Mosaic virus) and PolyA signals from nopaline synthase gene were introduced to Tobacco as well as Tomato cells were regenerated and resistance towards TMV were achieved.
Pesticide resistant plants- Pesticides are usually chemicals that affect the overall health of the plant itself. Growths of the plants are retarded on exposure towards them by blocking the amino acid synthesis, chemical interactions. To minimize the use of pesticides controlling the attack of insects could be achieved. An example is BT cotton, tomato etc. Resistance towards insects were achieved by the expression of insect toxin gene of Bacillus thurengensis in tomato , B. thurengensis produces Cry protein which acts as a gut toxin on consumption by the insects. pMON9711 with BT, 35S CaMV promoter, 3’ nopaline and neomycin phosphotransferase gene responsible for Kanamycin resistance property were transformed to tomato. As its toxic property is expressed only with the action of proteases. Modification was made to the technique by introducing cloned toxin gene via Ti plasmid into plants so that the plant itself could produce BT toxin. Recent researches have done on creating plants that kill insects by regulating their gene expression by gene-silencing response called RNA interference.
Herbicide resistant plants- Out growth of weeds could lead to insufficient nutrient supply, so growth of weeds are to be controlled hence herbicides are necessary for the survival of the plant. At the same time, these herbicides itself could be dangerous to plants as the biochemical properties of the herbicides could be harmful for the plant. Herbicides attack EPSP synthase (5 EnolPyruvyl Shikimate 3 - Phosphate), an essential enzyme for the production of aminoacid. Studies have shown that transformation of EPSP synthase from Arabidopsis with 35S CaMV promoter resulted in overproduction of EPSPs and to glyphosate tolerance in transformed callus.
Desired characters- Delayed ripening by gene silencing two ripening-specific N-glycoprotein modifying enzymes, α-mannosidase (α-Man) and β-D-N-acetylhexosaminidase (β-Hex) in tomatoes which assures its quality and freshness for 45 days. This characteristics put them in demand in commercial aspects. Nitrogen fixation by non-nitrogen fixing plants through transformation of nif genes. Traits like increased photosynthesis, early flowering, plants that can survive temperature variations, edible vaccines in short any traits in demand could be achieved through Genetic Engineering.
Advantages of GM:
Drawbacks
The major concern regarding GM crops are how safe they are for consumption. Though GM crops claim to be safe, experiments done on rats which were fed on GM maize (BT and Glyphosate resistant) showed statistically significant signs of liver, kidney damage, higher blood sugar levels and high triglyceride levels when compared to controls.
GM crops are with no doubt intended to be beneficiary but the real question is, should we expose ourselves to tentative techniques to gain something which we are unsure of??
Disease resistant plants- Resistance towards many viruses as well as fungus could be achieved. An expression vector with CaMV (Cauliflower mosaic virus) 35S promoter, cDNA of TMV(Tobacco Mosaic virus) and PolyA signals from nopaline synthase gene were introduced to Tobacco as well as Tomato cells were regenerated and resistance towards TMV were achieved.
Pesticide resistant plants- Pesticides are usually chemicals that affect the overall health of the plant itself. Growths of the plants are retarded on exposure towards them by blocking the amino acid synthesis, chemical interactions. To minimize the use of pesticides controlling the attack of insects could be achieved. An example is BT cotton, tomato etc. Resistance towards insects were achieved by the expression of insect toxin gene of Bacillus thurengensis in tomato , B. thurengensis produces Cry protein which acts as a gut toxin on consumption by the insects. pMON9711 with BT, 35S CaMV promoter, 3’ nopaline and neomycin phosphotransferase gene responsible for Kanamycin resistance property were transformed to tomato. As its toxic property is expressed only with the action of proteases. Modification was made to the technique by introducing cloned toxin gene via Ti plasmid into plants so that the plant itself could produce BT toxin. Recent researches have done on creating plants that kill insects by regulating their gene expression by gene-silencing response called RNA interference.
Herbicide resistant plants- Out growth of weeds could lead to insufficient nutrient supply, so growth of weeds are to be controlled hence herbicides are necessary for the survival of the plant. At the same time, these herbicides itself could be dangerous to plants as the biochemical properties of the herbicides could be harmful for the plant. Herbicides attack EPSP synthase (5 EnolPyruvyl Shikimate 3 - Phosphate), an essential enzyme for the production of aminoacid. Studies have shown that transformation of EPSP synthase from Arabidopsis with 35S CaMV promoter resulted in overproduction of EPSPs and to glyphosate tolerance in transformed callus.
Desired characters- Delayed ripening by gene silencing two ripening-specific N-glycoprotein modifying enzymes, α-mannosidase (α-Man) and β-D-N-acetylhexosaminidase (β-Hex) in tomatoes which assures its quality and freshness for 45 days. This characteristics put them in demand in commercial aspects. Nitrogen fixation by non-nitrogen fixing plants through transformation of nif genes. Traits like increased photosynthesis, early flowering, plants that can survive temperature variations, edible vaccines in short any traits in demand could be achieved through Genetic Engineering.
Advantages of GM:
- Improves nutritional quality
- Offer disease resistance
- Environment friendly- by reduced usage of pesticides
- Therapeutical values
- Longer shelf lives
- Availability- despite the seasonal barriers.
Drawbacks
- Environment pollution by genetic variants
- Developing herbicide pesticide resistant weeds and pests.
- Unintended harm to butterflies and other organisms.
- Accumulation of ‘unnatural’ elements in the environment.
- Therapeutical values like incorporating vitamins might lead to over dosage.
- Uncertain health hazards towards antibiotic resistance genes and other inserted elements.
The major concern regarding GM crops are how safe they are for consumption. Though GM crops claim to be safe, experiments done on rats which were fed on GM maize (BT and Glyphosate resistant) showed statistically significant signs of liver, kidney damage, higher blood sugar levels and high triglyceride levels when compared to controls.
GM crops are with no doubt intended to be beneficiary but the real question is, should we expose ourselves to tentative techniques to gain something which we are unsure of??
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