Question

describe the four mechanisms currently used to create genetically modified organisms.

Answer 1

Answer : Genetic Modification: It refers to the insertion of a foreign DNA fragment containing gene of interest into the genome of the plant in order to express some specific characters (e.g. resistance, over-production etc.). There are many techniques used for genetic modification, some are as follows:

1. Agrobacterium mediated gene transfer: Agrobacterium tumifaciens is a soil dwelling bacterium. It causes a disease called crown gall disease in plants. It is used as a biological vector to transfer the DNA construct in plants due to its DNA transfer mechanism. During genetic modification procedure the disease causing ability of bacterium is being shut down. The plant cells and bacterium co-cultivated in a petri plate under the conditions that facilitate gene transfer. This allows the incorporation of DNA into the plant cells.

2. Electroporation: This technique is also known as electropermeability. In this technique, electric field is applied across the cells to be inserted with DNA. Electric pulse increases the permeability of the cells which facilitate the uptake of DNA insert.

3. Gene Gun: In this method, microscopic pellets of gold or tungsten are coated with the transgene fragment and shot at high velocity into plant cells or tissues. In a small proportion of cases, the pellet will pass through the cells and the DNA fragment will remain behind and become incorporated into a plant chromosome in the cell nucleus.

4. Microinjection: In this method, the DNA fragment is inserted into the plant cells with the help of glass micro needles. Plant cells are held with the help of suction tube and DNA fragment is inserted by puncturing the plant cells and inserting the DNA fragment.