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Methods of genetic modification of organisms

In order to genetically modify an organism (e.g. make bacteria produce insuline), first from the organism that produces this hormone, a fragment which codes the right protein needs to be cut out. The cut out DNA fragment is then placed in the genetic vectorgenetic vectorgenetic vector, which can be a virus or a plasmidplasmidplasmid. Plasmids are nucleic acid molecules that occur in a bacterial cell outside its „chromosome” and are capable of self‑replication. Such a vector is introduced into a recipient organism (e.g. bacterial cell) that synthesizes proteins encoded in the introduced DNA.

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Ilustracja przestawia dwie fioletowe struktury z wypustkami, oznaczające wirusy. Po prawej ukazano roślinę z korzeniami w glebie. W pierwszym wirusie znajduje się pomarańczowa linia, oznaczająca jego DNA. W drugim wirusie pomarańczowa linia ma zieloną wstawkę, czyli obcy gen. Czerwona strzałka wskazuje wprowadzenie zmodyfikowanego wirusa do rośliny. Zaczyna ona produkować obce białka.

Another possibility of introducing foreign DNA into a cell is electroporationelectroporationelectroporation. This method uses a series of electrical impulses which create pores in the cell membrane through which the foreign DNA can penetrate the cell intended for the genetic modification. Electroporation is also used in cancer treatment, when the medicine cannot penetrate the tumor.

Biolistic transfromationbiolistic transfromationBiolistic transfromation is a method involving introduction of small balls (usually gold or tungsten) coated in DNA, which serve as bullets. These balls accelerated to high speeds (up to several m/s) by the so‑called gene gungene gungene gun penetrate the cell membrane and enter the cell, introducing the foreign DNA material. These bombed cells are being grown. After a certain period of time, it is checked if the DNA has been built into the genome. Unfortunately, the biolistic transfromation is a flawed method –gene guns are expensive and the method itself is not effective, as it causes mechanical damage to the cells.

Use of genetically modified organisms

Biotechnology uses microorganisms to produce proteins, hormones and vitamins. Currently, yeasts which have the gene responsible for the production of insulin (obtained by genetic engineering) are used to produce one of the human hormones – insulin, which regulates the blood sugar level.

The human growth hormone is another example of a substance produced using genetically modified microorganisms. This hormone is administered to children suffering from dwarfism, whose pituitary gland does not produce enough of the hormone. This prevents the development of the disease or reduces its effects.

Another substance which is produced thanks to the genetic modification is hirudinhirudinhirudin – a substance produced by leeches, which reduces blood clotting. It is used when patients suffer from thrombosis or vascular embolism. It prevents platelets from sticking together and eliminates clots that block the blood flow and cause oedema. The possibility of transferring the gene responsible for production of hirudin from leeches to microorganisms allowed the industrial production of this medicine.

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Fotografia przedstawia jasnozielone sadzonki sałaty na grządce. Jej liście zawierają szczepionkę przeciw wirusowemu zapaleniu wątroby typu B.

The ability to create vaccines is one of the most important use of the genetically modified organisms. In 2013 first influenza vaccine was created which contains proteins derived from insect cells. The time needed to produce such a vaccine was much shorter than that needed for previous methods, which is immensly important when the influenza virus undergoes numerous mutations. Professor Andrzej Legocki bred in Poland lettuce, which contained the vaccine against Hepatitis B (HBV). In order to obtain it, he used the bacteria causing plant diseases, which enables the insertion of foreign DNA into a plant genome. Using this bacteria, he inserted the genes coding the proteins, which appear on the surface of the Hepatitis B virus, in the lettuce genome. The first phase of the research was carried out on mice, which ate the genetically modified lettuce. This way the mice received substance which helped them fight the infection caused by the HBV and avoid it.

Summary

• In order to insert foreign genes into cells, various cloning‑based and non‑cloning methods are used.

• by using microorganisms it is possible to produce useful substances (e.g. medicine)

Keywords

microorganisms, plasmid, cloning vector

Glossary