Genetic engineering is a technique used to transfer useful genes from one organism to another for attaining a specific benefit for mankind. You have already studied it in detail in chapter 17.

20.1.1 Transgenic bacteria and the preparation of insulin

One of the proteins formed by the process of genetic engineering is insulin. Insulin is a hormone produced by our bodies, which control the amount of sugar in the blood. People, unable to make insulin suffer from the disease “diabetes mellitus”. They are unable to store glucose as glycogen but excrete it in their urine. Insulin is used to treat such patients. Insulin produced by genetic engineering is exactly the same as ordinary human insulin.

“Any organism which acquires a foreign gene is called transgenic organism”.

production of insulin

Fig. 20.1 the introduction of human gene into a bacterium abd production of insulin

Genetic engineering is of great importance and has application in agriculture, chemical &drug industries and medicine.

20.1.2 Biotechnology

Biotechnology is a large-scale industrial use of biological processes of microorganisms to make substances useful for mankind. The term ‘biotechnology’ was introduced in 1970’s.biotechnology is usually linked to genetic engineering and is involved in the production of specific products (e.g. enzymes and hormones) by genetically engineered organisms (fig.20.1).

The ability of microorganisms to carry out fermentation has long been used to produce foods such as bread, cheese and yogurt. Some other examples of the use of biotechnology are production of antibiotics, single cell proteins and fertilizers.


It is a catabolic process in which partial degradation of sugar occurs without the help of oxygen. Lactic acid fermentation by certain fungi and bacteria is used in the diary industry to make cheese and yogurt. Alcoholic fermentation is the second type of fermentation. A cetone and methyl alcohol are the by-products of this fermentation. These are commercially important. In baking industry brewing is carried out by yeast.

 genetic engineering

In bread making, the flour used contains starch, protein and an enzyme amylase. The flour is mixed with water to form dough. Amylase digests the starch into glucose. Lack of O2 inside the dough causes the yeast to respire anaerobically. As a result glucose is fermented to alcohol and CO2 the CO produced causes the dough to rise and because of this, cavities appear. Alcohol produced evaporates during baking (fig 20.2)


Fig 20.2 CO2 produced by the yeast causes dough to rise