Dr VISHAL SHARMA Assoc. Proff Government Post Graduate College For Girls-11,Chandigarh

1. GENETICALLY MODIFIED CROPS Dr VISHAL SHARMA Assoc. Proff Government Post Graduate College For Girls-11,Chandigarh

2. What is Genetic Modification? Genetic modification involves altering an organism's DNA.This can be done byaltering an existing section of DNA, or by adding a new gene altogether.A gene is a code that governs how we appear and what characteristics we have.Like animals, plants have genes too. Genes decide the colour of flowers, and how tall a plant can grow. Like people, the characteristics of a plant will be transferred to its childrenthe plant seeds, which grow into new plants

3. Genetic modification of plants occurs in several stages: 1. An organism that has the desired characteristic is identified. 2. The specific gene that produces this characteristic is located and cut out of theplant’s DNA. 3 To get the gene into the cells of the plant being modified, the gene needs to beattached to a carrier. A piece of bacterial DNA called a plasmid is joined to thegene to act as the carrier. 4. A type of switch, called a ‘promoter’, is also included with the combin- ed gene and carrier. This helps make sure the gene works properly when it is put into the plant being modified. Only a small number of cells in the plant being modified will actually take up the new gene. To find out which ones have done so, the carrier package often also includes a marker gene to identify them. How does a genetic scientist work?

5. 5. The gene package is then inserted back into the bacterium, which is allowed to • reproduce to create many copies of the gene package. • 6. The gene packages are then transferred into the plant being modified. This is • usually done in one of two ways: • By • attaching the gene packages to tiny particles of gold or tungsten and • firing them at high speed into the plant tissue. Gold or tungsten are used • because they are chemically inert – in other words, they won't react with • their surroundings • By • using a soil bacterium, called Agrobacteriumtumefaciens, to take it in • when it infects the plant tissue.

7. Golden riceGolden rice is genetically modified rice that now contains a large amount of A-vitamins. Or more correctly, the rice contains the element beta-carotene which is converted in the body into Vitamin-A. So when you eat golden rice, you get more vitamin A. Beta-carotene gives carrots their orange colour and is the reason why genetically modified rice is golden. For the golden rice to make beta-carotene three new genes are implanted: two from daffodils and the third from a bacterium. • Advantages: • The rice can be considered a particular advantage to poor people in underdeveloped countries. They eat only an extremely limited diet lacking in the essential bodily vitamins. The consequences of this restricted diet causes many people to die or become blind. This is particularly true in areas of Asia, where most of the population live on rice from morning to evening. • Disadvantages: • Critics fear that poor people in underdeveloped countries are becoming too dependent on the rich western world. Usually, it is the large private companies in the West that have the means to develop genetically modified plants. By making the plants sterile these large companies can prevent farmers from growing plant-seed for the following year - forcing them to buy new rice from the companies. • Some opposers of genetic modification see the "golden rice" as a method of making genetic engineering more widely accepted. Opponents fear that companies will go on to develop other genetically modified plants from which they can make a profit. A situation could develop where the large companies own the rights to all the good crops

8. FLAVR SAVR™ tomatoes were developed using recombinant DNA techniques to express the trait of delayed softening of tomato fruit. The novel variety was developed by insertion of an additional copy of the polygalacturonase (PG) encoding gene in the “antisense” orientation, resulting in reduced translation of the endogenous PG messenger RNA (mRNA). The antisense PG gene is essentially a reverse copy of part of the native tomato PG gene that suppresses the expression of endogenous PG enzyme prior to the onset of fruit ripening. The mechanism of decreased PG activity in FLAVR SAVR™ tomato is likely linked to the hybridization of antisense and sense mRNA transcripts, resulting in a decreased amount of free positive sense mRNA available for protein translation. Reduced PG expression decreases the breakdown of pectin and leads to fruit with slowed cell wall breakdown, better viscosity characteristics and delayed softening. FLAVR SAVR™ tomatoes have improved harvest and processing properties that allow the transgenic tomatoes to remain longer on the vine to develop their natural flavour, maintain firmness for shipping and produce a thicker consistency in processing.

9. Modification Method • This bioengineered tomato was produced by Agrobacterium-mediated transformation of tomato (Lycopersiconesculentum) in which the transfer-DNA (T-DNA) region of the bacterial tumour inducing (Ti) plasmid was modified to contain DNA sequences encoding an “antisense” PG gene construct and the NPTII encoding neo gene from E. coli K12. During transformation, the T-DNA portion of the plasmid was transferred into the plant cells and stably integrated into the plant's genome. The antisense PG gene was under the regulatory control of a single copy of the 35S promoter from the cauliflower mosaic virus (CaMV), or two tandem copies of the 35S promoter. The terminator sequences were from the tml gene and the transcript 7 gene from the octopine-type Ti plasmid pTiA6 from A. tumefaciens. Expression of the neo gene was under the control of the 5' promoter and 3' terminator sequences from the mannopinesynthase gene derived from A. tumefaciens.