Genetic Engineering

Genetic engineering involves the extraction of a gene from one living organism and inserting it into another organism, so that the receiving organism can express the product of the gene.

A basic technique used is the genetic engineering of bacteria. It can be broken into the following key stages:

  1. Selection of characteristics.
    Identifying the gene from amongst all the others in the DNA of the donor organism.
  2. Isolation of the gene.
    Obtaining a copy of the required gene from the DNA of the donor organism and placing it in a vector.
    (A vector in biology refers to an organism that acts as a vehicle to transfer genetic material from a donor organism to a target cell in a recipient organism.)
  3. Insertion
    Use the vector to introduce the gene into the host cell.
  4. Replication
    Allow the host cell to multiply to make multiple clones of the genes.


Example of Genetically Engineered Bacteria – Production of Human Insulin

An example of genetically engineered bacteria is in the production of human insulin. Insulin is a protein hormone produced in the pancreas which has an important function in the regulation of blood sugar levels. Insulin facilitates the transport of glucose into cells. A deficiency in insulin is one of the causes of the disease diabetes mellitus or sugar diabetes in which the sugar levels in the blood become raised resulting in harmful consequences. At least 3% of the world’s population is affected by diabetes mellitus and sufferers of the disease require insulin injections to manage the disease.



Before genetic engineering, insulin used for treatment was sourced from the pancreas of slaughtered pigs and cattle. This source of insulin had minor differences in the amino acid composition to the insulin produced in humans and also contained trace impurities. As a result some patients were allergic to insulin sourced from animals and had damaging side effects as a result of treatment from these injections. The solution to this problem was solved by genetic engineering.


The animation below shows how human insulin is produced by genetic engineering.



The process of genetically engineering insulin on the large scale takes place in bioreactors. These are large vessels usually constructed from stainless steel in which the bacteria are grown. They are also referred to as fermentation vessels as they provide the correct nutrients and controlled conditions in which the bacteria can grow and multiply rapidly. For insulin production the bioreactors are strictly controlled and kept in clean environments. On completion of the fermentation cycle the insulin is extracted and purified.