There have been few issues related to modern agriculture that have been quite so contentious as that of Genetic Modification and with the media portraying dramatic images of "frankenstein foods", it has been little wonder that opinion has been so polarised. And yet on the whole subject there is widespread ignorance; in a recent survey over half of all respondents thought that genes were only contained in genetically modified material. We consider the origins of genetic modification and the biotechnology revolution.

Ever since the start of farming over 10,000 years ago, man has sought to find ways of making his crops and livestock more productive. Innovations in mechanisation and farming systems have been combined with the deliberate selection of crops or livestock for "improved" characteristics.

The result of this selection can be seen in the obvious differences between a primitive sheep breed, pictured above, and its modern successor alongside. The improved characteristics of the modern sheep include: its willingness to be flocked and driven, its docile nature, higher lambing output and the production of more meat and wool.

The selection that has resulted in the modern sheep may have arisen either by accident or through design. A farmer may have noticed a particular characteristics in some of his of sheep that was desirable and therefore retained these animals. Alternatively he may have actively crossed sheep of very different charcteristics to see if an improved characteristics would result.

In much the same way that sheep breeds have been improved through selection, so the same has occurred with crop varieties. Crops that suffer less from disease, which are more drought resistant or which produce grain of a higher quality are constantly preferred. In being preferred, they remain in use for both production and future breeding.

The characteristics that we define in crops or livestock (for example disease resistance or wool quality) are often known as traits and these are conferred by something known as genes. Genes either act singly or collectively to confer a trait. Some traits will persist in a population for a long time, for example wool quality whereas some may disappear quickly - disease resistance in crops can be lost as fungi find new ways of attacking the plant.

Genes are found on chromosones that exist within every cell of every living organism. Each organism contains a selection of unique genes that confers it with sufficient differences to make it recognisable as a species, for example a cow or a sheep, whereas the arrangement and characteristics of a number of other genes confers differences between members of the same species.

During the process of reproduction, a copy of the genes from each parent are passed down to the offspring. In this process the genes get mixed up before being laid out on the offspring's chromosones. The new mix of genes determines the specific or distinguishing characteristics of the offspring.

Within the last decade advances in biotechnology have allowed mankind to identify the specific genes that cause specific traits. The technology has further provided man with the ability to artificially transfer genes from one chromosone to another, even if this is across the species barrier. Thus, a gene from a plant that is resistant to insect attack can be transferred to a different species of plant that would normally be susceptible. This is the process of genetic modification and the new crop will be known as a transgenic crop.

Whilst the transfer of genes across species has been condemned by some religious communities, most species already share a very significant amount of common genetic material. In the case of man and the chimpanzee, 99.4% of this is common.

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