Biolistics
Biolistics is also a commonly used method for genetic transformation of plants and other organisms. It is the coating of molecules, either nucleic acids or other biological molecules, intending on being introduced into cells, using either gold or tungsten micro-particles. Then using a gene gun, the cell gets penetrated through the cell wall and membrane and into the cell.
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Agrobacterium
Agrobacterium is a small bacterial rod that can reduce nitrates and cause galls on plant stems. the ability to introduce new genetic material into the plant cell, in this case, the soybean plant cell. Agrobacterium tumefaciens (meaning tumour-making), can infect wounded plant tissue, transferring a Ti plasmid to the plant cell. Part of the Ti plasmid migrates into the chromosome of the plant. The migrated Ti plasmid contains genes for the synthesis of food for the bacterium, and plant hormones. Genes from the Ti plasmid that are integrated in the plant chromosome are expressed at high levels in the plant. Overproduction of the plant hormones leads to continuous growth of the transformed cells, causing plant tumours. Rapid, cancerous growth of the transformed plant tissue which is advantageous to the bacterium as more food gets produced.
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Electroporation
Electroporation is a technique used to increase the permeability of the cell membrane, allowing DNA, chemicals or drugs to ne introduced into the cell. Electroporation uses an electrical pulse to introduce new species into cells. The technique exploits the weak interactions between phospholipid bilayers that maintain the integrity of cell membranes. Under the right conditions, the channels of the phospholipid bilayer rapidly close, returning the cell to its original state, except that the cell now contains foreign molecules.
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Genetically modifying animals:
Genetic engineering is a targeted and powerful method of introducing desirable traits into animals using recombinant DNA (rDNA) technology. DNA is the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.
Methods that are used for genetically modifying animals are: Microinjection- DNA is injected into the nucleus of a single cell embryo using a very fine needle. Between 200 - 500 copies of the gene are injected into each embryo. Viruses - Used as 'vectors' to introduce new genetic material into cells. Retroviruses are a type of virus which replicates by integrating itself into the host DNA and is then copied with the host genetic material as the cell divides. Sperm mediated transfer - Using genetically modified sperm as a vector for introducing foreign DNA into the egg has obvious attractions as artificial insemination of livestock and poultry is routine. |