Understanding Biotechnology

What is Biotechnology

Overview of Biotechnology

History of Biotechnology

Why do we do biotechnology?

Biotechnology for the environment

Biotechnology for food and agriculture

New genes can be inserted into plant, animal and bacterial cells in several different ways.

Transferring genes to bacteria

Calcium chloride treatment involves placing the bacteria and the bacteria with the new gene in them in an ice-cold solution containing calcium chloride.

The calcium chloride changes the nature of the cell wall, allowing the new DNA to enter the cells more easily. The cells are then 'heat shocked' by heating to 42°C in a waterbath for 2 minutes. The heat shock causes the cells to take up the plasmid with the new DNA.

The cells are returned to normal growing conditions so that they can recover and the new gene begins to function within the cell.

Transferring genes to plants

The new DNA is first transferred to the circular DNA molecules called plasmids which are found within bacteria. When the bacteria infects the plant cells, the new DNA enters the plant cell.

Transferring genes to plant, animal and yeast cells

The cells are placed in a solution with the new DNA that is to be added. The solution is then subjected to a high voltage electric shock for a fraction of a second. This causes small holes to form in the cell membrane, through which DNA can enter.

The cells are then placed in a nutrient solution, allowing them to repair their membranes and cell walls and recover their normal functions.

The egg cell containing the new DNA is implanted into a female animal. Because the gene was inserted into the DNA at the egg stage, when the cell divides, every cell in the growing embryo will contain the new DNA.

• Calcium phosphate precipitation and phagocytosis: used to transform cells of mammals. Only about 1-2 per cent of cells are transformed, so it is not a particularly efficient procedure. The DNA to be transferred is mixed with calcium phosphate. The DNA and the calcium phosphate react to form tiny solid grains. The cells engulf the grains in a process called phagocytosis (how amoebas eat their food). Some of the new DNA becomes a part of the cell's DNA.
   
• Lipofection: used to transform cells of animals, yeast, plants and bacteria. Plant cells are first treated to remove their cell walls. The DNA to be transferred is placed into liposomes, which are special kinds of fats that form tiny hollow bubbles. The cells to be transformed are added to the solution containing the liposome bubbles. Since the liposomes are made up of lipids, they become part of the cell membrane of the cells and the contents - the new DNA - enters the cells

• Biolistics: used widely in the production of genetically modified corn, and also in the genetic immunisation of animals. Tiny tungsten or gold particles are coated with the DNA to be transferred. The particles are usually about 0.004 of a millimetre in diameter. A blast of high-pressure helium gas or gunpowder shoots the particles carrying the DNA into the cells that are to be transformed.
   
• Viruses as carriers: used to transform cells of plants and animals. It is not a commonly-used technique. A virus is chosen that will enter the cell to be transformed but not kill it. The DNA to be transferred is added to the virus DNA. The virus injects its DNA, including the new DNA, into the cell.