It is 2095 and time Sharon's Mum told her the facts of life. On the first day of National Science Week, Tom Wilkie steps into a future of genetically fabricated families
For Trevor and Tracy, it was the moment every parent finds difficult. Sharon, their eldest, had started asking The Question: where did I come from, Mummy? As she patted her daughter's blond hair (catalogue number: HC 205) and looked into her perfect cornflower blue eyes (EC 317), Tracy decided that, in 2095, there was nothing to be squeamish about.

Sharon had heard disturbing rumours about how in the old days, when a man and a woman wanted to have a baby, they went to bed with each other and left the outcome to passion and chance. Well, this was not the way her father and mother had set about bringing their daughter into the world, Tracy assured her.

It was virtually inconceivable that any responsible parent could permit a child to be born whose genes had been left to the chance shuffling of natural processes, although there were rumours of underground groups that still practised "chance childbirth" as it was called. No, that was quite obscene. No parent would allow a foetus to go through nine months of development without knowing the colour of its eyes, or whether it had straight hair or wavy. Good grief, no one would ever conceive a child without specifying the genes for its intelligence quotient, which would help determine its chances in education and subsequent employment.

No, Sharon had to understand that Trevor and Tracy had been thorough. They had gone to the Ideal Baby exhibition at Olympia and they had combed through months of back issues of Genes and Babies magazine. They had window- shopped hopefully at the Harrods' Baby Counter (but the prices were prohibitive) and had leafed carefully through the glossy pages of a Swedish genetic superstore's DNA Catalogue for novel ideas. They would have liked to go to one of the specialist gene designers, who trawled the world's gene banks, for the most exotic mixtures and the latest models. In the end, though, Trevor was only a relatively humble virtual manager and they could afford only to go along to their local mass-retailer, the Genes `R' Us supermarket to choose Sharon's genes.

All children these days were put together according to their parents' specifications. And, of course, Trevor and Tracy would have sent back any baby which did not conform to their wishes. The right of return with full refund had been written into the recent Consumer Protection (Human DNA) Act. The Act was passed after a long debate following a couple of controversial High Court cases in which the judges (such old men, and so completely out of touch with the modern world) had ruled that any human baby merited the law's protection whether it met the parents' specification or not. Their rulings had met with a howl of protest from parents insisting that the gene-retailers and baby farmers should be forced to keep to their contracts.

As Colchester's Anglican vicar, Tracy felt she had a moral duty to explain to her daughter the facts of life. (Married women had been at a premium in the Church since the schism following the great "gay synod" of 2004.)

Tracy explained that the "blueprint" for all living things, plants and animals alike, is contained in a substance called DNA. The set of instructions which tells a fertilised egg that it is to develop into a human being and not a chimpanzee is written out in chemical letters along the DNA. Family resemblances arise, Tracy explained, because children inherit their DNA from their parents, transmitted in the egg and sperm. Or at least that was how matters had been before technology and civilisation had allowed parents to choose their child's genetic inheritance at will. That was why Sharon had fair hair, blue eyes and creamy-pink skin whereas her mother and father both had brown eyes, dark skin and hair.

But the Church paid its priests poorly and there had been a recession at the genetically engineered food factory where Trevor worked, so, Tracy reflected, it might be better not to mention the fact that they had not been able to afford the most expensive high intelligence genetic profile for Sharon. Over the previous two decades, high intelligence genes had been hoarded by a giant Chinese corporation, which traded under the name GeneSoft. Prices had been driven beyond the reach of ordinary consumers like Trevor and Tracy.

They had settled for a cheaper model (catalogue number: IQ 200). Sharon would therefore always be less intelligent than her school-friend Charlotte, whose grandparents had taken out a second mortgage to help purchase for her the genes guaranteeing ultra-high intelligence (catalogue number IQ 300). And because Charlotte's grandfather had been a geneticist, they had been able to get a trade discount.

Sharon could learn the realities of the market economy later, Tracy decided; for the moment she would have to stick to the facts of biology to tell Sharon about the history of human reproduction and genetics. She settled Sharon down in front of their Netscreen module and told it to call up the history service, which then through holographic clips, graphics and 3D-images began to explain how society had put scientific knowledge to use to arrive at the genetic superstores of 2095.

The first step on the road away from superstition and towards the decency of the 21st century came in the 1960s, when The Pill first became available. For the first time in history, women were freed from the burden of biology and could choose when to have a baby.

Technology moved on very quickly, the Netscreen virtual environment explained, using dated television news clips from 1978 to tell the story of Louise Brown, the world's first test-tube baby. The technique, "in vitro fertilisation" offered another way for people to take control of their biology. IVF meant a woman could carry in her womb a child to which she bore no genetic relationship.

In 1985, Britain's first commercial surrogate mother, Kim Cotton, was paid £6,500 to have an American couple's baby. By 1993 Italian doctors had implanted a fertilised egg, donated by a white woman, into the womb of a black woman, thus altering one of the most firmly established of all inherited traits: that a child should resemble its parents. Now prospective parents could choose the skin colour and racial grouping of their offspring.

Yet something far more profound was going on elsewhere. At a cost of more than $3bn, scientists in the major developed countries were sifting through the human genome: the compendium of all the genes in humanity's inherited blueprint. When this international Human Genome Project was complete, scientists had read the set of instructions written in DNA : they began to rewrite it as well.

On 14 September 1990, doctors at the US National Institutes of Health near Washington DC conducted the first successful attempt to treat disease by transplanting human genes a four-year-old girl who suffered from an inborn defect of her immune system that had left her defenceless against infection. Within weeks of her gene therapy, the girl was going dancing and taking skating lessons, without fear of infection.

At that point Trevor returned from work. As she saw him Tracy felt, as always, joy that he was still alive. In an unpleasant incident at work involving the plutonium and the cobalt-60 source of gamma-rays, Trevor's spleen, liver and kidneys had been destroyed. But the two of them were fortunate that they had taken out extra health insurance to cover genetic engineering of a pig, which was bred to provide organs suitable for transplant and which were virtually guaranteed not to be rejected by Trevor's immune system.

Trevor and Tracy had made sure that, when Sharon was born, they had invested in breeding a line of customised pigs containing copies of Sharon's genes in case she needed organ transplants later.

Yet science was not the only force at work. Commerce became increasingly powerful. Commerce was at the forefront of the Human Genome Project. Many genetics researchers in the USA and several in Britain were directors of private biotechnology companies, while receiving research grants from public funds or from charities. It was the greatest privatisation programme of the 21st century: the privatisation of DNA.

The scientific power of the new genetics, to fabricate what was previously seen as natural, was harnessed not by the public sector but by the market and giant corporations. Genetic engineering research had led to prototypes, which had led to production for general consumption. Soon the genetics industry was following the same path of software, information technology and semi-conductors in the 20th century. The huge R&D costs had to be covered by worldwide sales. Those were the commercial and scientific roots of the genetics superstores of 2095.

"All very interesting", said Sharon, wriggling on the sofa, "but Neighbours will be on in a minute, can't you just tell me where I came from?" Tracy wondered why they hadn't spent a bit more money to get one of the higher- powered patience genes that had just come on the market. So she told her daughter the story.

By the middle of the 21st century advances in science had produced female gorillas with a virtually human reproductive system. So a human egg fertilised in vitro could be implanted in the uterus of such a gorilla. That was how Sharon had been born. After Tracy and Trevor had chosen her genes, they had come back to Genes `R' Us nine months later to pick up their new child which had been nurtured in the surrogate womb of a genetically engineered female gorilla. Tracy, happily, was spared the bother and inconvenience of having to be pregnant or the difficulties and pain of birth.

On 23 March, the `Independent' is holding a public debate at the Institute of Education in London on `Monster Myths: are writers demonising the new genetics?' Tickets (£10) available by phoning 0171-611 8442.