This hypothetical question is about to come true some time in the next couple of months, all over the supermarkets and food shops of Britain, and anywhere else in Europe that allows it - except that the genetically engineered loaves won't be blue, nor will there be a label to tell you which loaf is which. It's conceivable - likely, in fact - that every loaf in the store will have some genetically engineered contents. You simply won't know, and the stores won't be able to tell you.
It's not just the loaves, either: 60 per cent of the products in the supermarket - anything including soya or soya oils or extracts, including such staples as margarines, biscuits, cakes, sauces, noodles, pies, cooking oils, salad dressings and pizza bases, will also contain genetically engineered soya or its extracts.
Is that bad? Up to 85 per cent of European consumers think so: they say they would like to know if food has been genetically modified. Understandably. They would be eating something that their bodies had never encountered before, something that could not arise in nature. Environmentalists and scientists argue that the stretches of DNA which confer the herbicide resistance could interact with bacteria in the gut to produce strange new hybrids with unpredictable properties.
Is this worry well founded? Such jumps do happen; it's part of the mysteries of genetics. Nobody knows the full story of how genes truly operate and interact. The science journal Nature commented in an editorial last week that such a sequence of events has "a low probability. But the risk, nevertheless, is there, and a matter of genuine scientific debate."
We will have no chance to debate the matter. Scientists, shopping chains and consumers will have the changes imposed on them by a combination of commercial steamrolling and government and consumer apathy.
The stores aren't actually very happy about this. All the major supermarkets pledged earlier this year that they would always label genetically engineered foods, so that customers would know what they were buying. When tomato puree made from tomatoes genetically modified to stay fresh longer (by switching off an enzyme-producing gene) went on sale in February, it was proudly labelled. One supermarket proclaimed: "If Sainsbury's are to sell further products developed with the aid of genetic modification, these will be labelled."
Eight months later, they are beating the retreat. "We have been forced to accept that we won't be able to label [soya products] separately," said a spokeswoman for Sainsbury's recently.
The problem is, they don't have any way to prevent it. The soya is being grown on the other side of the Atlantic, and will this year make up about 2 per cent of the harvest. The powerful American Soybean Association has decided that it would be too expensive for its members to separate out the genetically engineered crop, and so it is all going into the same hopper. It's a multibillion-dollar industry, and the concerns of a few scientists not on their payroll, and of some environmental pressure groups, are not going to sway them.
It doesn't stop there. Ciba-Geigy, the Swiss giant, has developed a form of maize that has been genetically altered to produce a chemical that poisons a troublesome mite called the corn borer, which normally chews out the stalks of the young crop. It is lobbying hard to have it accepted for wider use.
However, the maize has not been approved by the EU Council of Environmental Ministers. The UK's Advisory Committee on Novel Foods and Processes was concerned by the addition to the maize of a gene that confers resistance to ampicillin, a widely used antibiotic. It argued that the gene could jump to the gut bacteria of animals that ate the unprocessed corn. The result would be bacteria resistant to ampicillin.
Europe may ban the US soya imports but that could trigger a small-scale trade war. So, at present, only Germany looks like it might take action, by finding alternative sources of standard soya.
Monsanto and Ciba-Geigy have hit back by finding scientists prepared to say that there is "no scientific data" to indicate that DNA could jump from food to a microbe in an animal's gut. Fine - except that once they said the same about BSE.
The core of the problem is that the food industry has grown so big that it has lost sight of what it exists to do: provide products that we all need to survive. In fact, companies such as Monsanto and Ciba-Geigy have begun to act as though people are a peculiar irritant to their achievement of their aims of making money from selling biological products to farmers.
There's an significant distinction between a foodstuff bred to grow larger, or a different colour, and one that has been genetically engineered to do so by adding another species' gene. Gardeners and farmers have managed the former for centuries, without resorting to high-tech laboratories.
But the new debate goes beyond even that. Genetic technology offers our best hope for understanding so much about ourselves and the world we live in - and consume. But it has to learn to distinguish between a tomato that has had one of its normal genes switched off, and one that has had a foreign one added to make it - in one case a chicken gene was added to a tomato to enhance its growth properties. Such a thing is no longer a tomato; it's a chimera which might not ever arise in nature. I'd like to know that before I bite into it.Reuse content