What is Genetic Engineering?

We find it mixed in our food on the shelves in the supermarket genetically engineered soybeans and maize. We find it growing in a plot down the lane, test field release sites with genetically engineered rape seed, sugar beet, wheat, potato, strawberries and more. There has been no warning and no consultation.

It is variously known as genetic engineering, genetic modification or genetic manipulation. All three terms mean the same thing, the reshuffling of genes usually from one species to another; existing examples include: from fish to tomato or from human to pig. Genetic engineering (GE) comes under the broad heading of biotechnology.

But how does it work? If you want to understand genetic engineering it is best to start with some basic biology.

What is a cell?

A cell is the smallest living unit, the basic structural and functional unit of all living matter, whether that is a plant, an animal or a fungus.

Some organisms such as amoebae, bacteria, some algae and fungi are single-celled - the entire organism is contained in just one cell. Humans are quite different and are made up of approximately 3 million million cells (3,000,000,000,000 cells).

Cells can take many shapes depending on their function, but commonly they will look like a brick with rounded comers or an angular blob - a building block.

Cells are stacked together to make up tissues, organs or structures (brain, liver, bones, skin, leaves, fruit etc.).

In an organism, cells depend on each other to perform various functions and tasks; some cells will produce enzymes, others will store sugars or fat; different cells again will build the skeleton or be in charge of communication like nerve cells; others are there for defence, such as white blood cells or stinging cells in jelly fish and plants.

In order to be a fully functional part of the whole, most cells have got the same information and resources and the same basic equipment.

A cell belonging to higher organisms (e.g. plant or animal) is composed of

* a cell MEMBRANE enclosing the whole cell. (Plant cells have an additional cell wall for structural reinforcement.)

* many ORGANELLES, which are functional components equivalent to the organs in the body of an animal e.g. for digestion, storage, excretion.

* a NUCLEUS, the command centre of the cell. It contains all the vital information needed by the cell or the whole organism to function, grow and reproduce. This information is stored in the form of a genetic code on the chromosomes, which are situated inside the nucleus.

Proteins are the basic building materials of a cell, made by the cell itself. Looking at them in close-up they consist of a chain of amino-acids, small specific building blocks that easily link up. Though the basic structure of proteins is linear, they are usually folded and folded again into complex structures. Different proteins have different functions. They can be transport molecules (e.g. oxygen binding haemoglobin of the red blood cells); they can be antibodies, messengers, enzymes (e.g. digestion enzymes) or hormones (e.g. growth hormones or insulin). Another group is the structural proteins that form boundaries and provide movement, elasticity and the ability to contract. Muscle fibres, for example, are mainly made of proteins. Proteins are thus crucial in the formation of cells and in giving cells the capacity to function properly.

Chromosomes means "coloured bodies" (they can be seen under the light microscope, using a particular stain). They look like bundled up knots and loops of a long thin thread. Chromosomes are the storage place for all genetic - that is hereditary - information. This information is written along the thin thread, called DNA. "DNA" is an abbreviation for deoxyribo nucleic acid, a specific acidic material that can be found in the nucleus. The genetic information is written in the form of a code, almost like a music tape. To ensure the thread and the information are stable and safe, a twisted double stranded thread is used - the famous double helix...