16.4 - Use of recombinant DNA technology

The genetic make-up of organisms can now be altered by transferring genes between individuals of the same species or between organisms of different species. These modifications can benefit humans in many ways including: 

• increasing the yield from animals or plant crops
• improving the nutrient content of foods
• introducing resistance to disease and pests
• making crop plants tolerant to herbicides
• developing tolerance to environmental conditions
• making vaccines
• producing medicines for treating disease

Examples of genetically modified microorganisms

• Antibiotics are produced naturally by bacteria. Although genetic engineering has not substantially improved the quality of antibiotics, it has produced bacteria that increase the quantity of the antibiotics produced and the rate at which they are made.
• Hormones - with genetic engineering, bacterial cells have the human insulin gene incorporated into them and so the insulin produced is identical to human insulin and has no adverse effect on the patient. This method also avoids killing animals and the need to modify insulin before it is injected into humans. Other hormones produced in this way include human growth hormone, cortisone, testosterone and oestrogen.
• Enzymes - includes amylase to break down starch during beer production, lipase to improve the flavour of cheese and proteases to tenderise meat.

GM Plants

• Genetically modified tomatoes have been developed using the inseration of a gene. This gene has a base sequence that is complementary to that of the gene producing the enzyme that causes the tomatoes to soften. The mRNA transcribed from this inserted gene is therefore complementary to the mRNA of the original gene. The two therefore combine to form a double-strand. The prevents the mRNA from the original gene from being translated. The softening enzyme is therefore not produced. This allows the tomatoes to develop flavour without the problems associated with harvesting, transporting and storing soft fruit.
• Herbicide-resistant crops have a gene introduced that makes them resistant to a specific herbicide. When the herbicide is sprayed on the crops, the weeds that are competing with…