What are GMOs?

In order to understand genetic modification it is first necessary to understand that living things are made of building blocks called cells. Higher animals are made up of hundreds of thousands of cells (many of which are specialised such as muscle cells and nerve cells) while bacteria consist of a single cell. The outer casing of a cell is an envelope known as the cell membrane. At the centre of each cell are long chains of a complex chemical, known as DNA (deoxyribonucleic acid). These DNA chains form the genetic material of the cell. When cells divide during the growth of an organism the genetic material forms a blueprint to enable new cells to be formed. Thus the first step in cell division is the duplication of the genetic material to form a copy that migrates to one end of the existing cell. This end of the cell is then separated off to form a daughter cell, by the formation an additional sheet of membrane that divides the new copy of the genetic material from the original copy.

The genetic material contains all the information necessary to build all the components of a cell. This information is in the form of a chemical code. The basis of this code relates to the fact that DNA chains are made up of four different chemicals, known as nucleotides, linked end-on-end. These four different nucleotides form the four characters in the DNA code. It is the order of the nucleotides, which is different in each individual, that forms the molecular basis of the way in which information is passed from one generation to the next.

The information encoded on DNA is sub-divided into blocks known as genes. Thus a gene can be thought of as an individual segment of information that encodes one small part of the process of forming a cell. One way of explaining this is by using an analogy in which the total complement of genetic material in a cell is visualised as being a library covering the history of the world. Then according to this analogy each gene would correspond to a single book in this library. Each book alone would make some sense as it stood, for example there might be a book describing the reign of Cleopatra in ancient Egypt, but if this book was read in isolation it would give no picture of the whole story.

Genetic modification is the process of altering the DNA code in a cell that is being artificially grown in a laboratory. The purpose of doing this is that when this cell is cultured or allowed to develop into a complete organism the genetic modification will have resulted in it having new characteristics. Often genetic modification involves isolating the DNA encoding a single gene from one organism and inserting it into the genetic material of another organism. For example one application of genetic modification has been the production within bacteria of human proteins, such as blood clotting factor VIII, insulin and blood cell growth factors. Whilst these proteins are produced naturally within the human body they are only present in minute amounts making their purification for therapeutic use extremely difficult. Therefore, the ability to insert the genes encoding these proteins into bacteria has been an important step forward. It is now possible to produce industrial scale quantities by growing such modified bacteria at large scale in fermenters.