Genomic research is expected to identify more than 5,000 biological targets that can be treated by new drugs

And if there are fewer genetic diseases and fewer genetic drugs, then genetic patents may not be so valuable - the drugs barons may not get as much back for the billions of pounds they've paid for the exclusive rights to individual genes and the information they hold.

But even if one gene no longer equals one disease and one drug, there is still massive potential within those 30,000 human genes.

The expansion in our medicine cabinets and in the drugs industry will be truly staggering. Just contrast the last 100 years with what we expect in the next 100.

All the drugs discovered over the last century act on just 450 biological targets. In the next century, genomic research is expected to identify more than 5,000 biological targets that can be treated by new drugs.

The companies that make their money from genetics break down into three groups.

There are companies that try to discover the genetic code and then sell on their findings.

Then there are companies that make the picks and shovels for this scientific research, making the scientific tools used in the geneticists in their labs.

And there are the companies that make their money turning all this genetic information into drugs and medicines.

Genetic data

The biggest name in the collection and interpretation of genetic data is the best-known genetic company of them all - Celera Genomics.

Its scientists are one of the two groups of geneticists who discovered that we don't have that many more genes than a mouse.

The American gene sequencing company is run by the famous geneticist Dr Craig Venter, and is part of the Applera Corporation, which also owns the gene tools company once known as PE Biosystems.

The corporation is worth �1.7bn, and is listed on the Nasdaq. The firm is well liked by Wall Street analysts; with five teams telling their clients to buy the shares. Two of those teams of company watchers say their clients should stock up as quickly as they can.

The other big name in gene data is the Californian firm Incyte, which provides genomic content to the drug giants. This company, also Nasdaq listed, is worth just under �1bn, and the analysts at the Wall Street firm Merrill Lynch expect it to turn in 25% growth in revenues both this year and next.

Gene tools

The next cluster of companies are the gene tools firms. They either make the gene sequencing equipment that lets scientists map genes more quickly, or manufacture gene chips, electronic devices which hold and store the details of up to 40,000 genes.

Among these companies is the only big British name in the business - Nycomed Amersham, based in Little Chalfont, and listed on the London Stock Exchange with a market value of �3.6bn. Its gene tool business is supported by hefty revenues from its X-ray and ultra-sound businesses.

Many biotech firms gain huge revenue from making scientific equipment

The global number one for gene tools is the German company Qiagen, listed on the Nasdaq with a market value of �3bn. The company makes the reagents and kits that speed up the purification of DNA, and the analysts at Bear Stearns expect this market to grow by 15% a year; but the shares (at $31.87) are close to their 52-week high, and Merrill's analysts reckon they're fully priced right now, and should be given a clear berth.

The other big hitters in this area are three Nasdaq-listed stocks - the DNA kit maker Invitrogen, with a value of �2.5bn; the gene chip seller Affymetrix, worth �2.3bn; and the life sciences research kit maker Techne, valued at �0.75b.

Affymetrix gets a particularly good write up from the Wall Street company watchers; nine of them rate the firm a buy or a strong buy, three say hold the shares if you've got them, one says sell.

The manufacturing of gene sequencing equipment is a business that is expected to grow by 12% a year, but things may not be so rosy for the gene chip makers.

They're likely to face much tougher competition in the future, from electronic companies like Motorola and Hewlett Packard, who are already turning their attention to this area.

Software

Within the gene tools companies lurks a smaller, more specialised area - the sale of bioinformatic software which allows the drugs companies to interpret and analyse data from individual genes.

The two big names in this sub-sector are much smaller that the other companies so far, but the analysts expect great things.

GeneLogic has a market value of just �400m on the Nasdaq, and InforMax is worth just �169m on that exchange, but the analysts at Merrill Lynch and Bear Stearns regard the stock as good for the long haul.

That leaves the shop front of genomics - the companies that turn all this genetic information into drugs.

This includes companies like the long-established American biotech firm Genentech, worth a massive �20.6bn on the New York Stock Exchange, and with an equally weighty recommendation from the Wall street analysts - 17 teams say buy the stock, 4 say hold. No-one says sell.

The other firms in this field are its smaller rivals, Millennium Pharmaceuticals (worth �5.2bn), Human Genome Sciences (worth �3.9bn) and Isis Pharmaceuticals (worth just �320m). All three are Nasdaq listed.

As most of these firms are based and listed in the United States, it can be difficult and costly for UK investors to buy into them.

It is also a very risky investment; these are very volatile stocks, and can plunge or soar on the market's whim. Nasdaq's biotech index may have put on 45% in a falling market last year, but few shareholders in British Biotech will forget their beating in a hurry - the stock which was once the darling of the stock market has lost 95% of its value over the last few years.

Units to trust

But there are easier ways to buy into genomics, and they may be less risky too - investment funds.

A number of investment funds and unit trusts put much or most of their money into genomics. The longest standing one is Framlington Health, which has turned �100 into �540 in just 7 years. It invests in companies such as Impath, Cardinal Health, Cell Therapeutics and OSI Pharma.

On the rankings in Money Observer magazine, that makes it the fifth best performing fund out of 866 unit trusts.

But remember that just because it has done well in the past, that doesn't mean it will do well in the future. Past performance is no guarantee of future growth, as the adverts always tell us.

Other funds are available - they include CF Biotech Fund, which is mostly based in the US; 3i Bioscience, which invest one-third of its funds in UK companies; and Finsbury Life Sciences, which puts 45% of its money in the UK, and the rest in continental Europe and Israel.

Protein companies

Of course, if we humans have fewer genes, maybe we should turn our attention away from pure gene companies.

Just as the geneticists were telling us that most of the biological action is now likely to be in protein synthesis rather than in the genes, the analysts in the City were telling us to look instead at companies that produce antibodies - proteins that can be used to target disease at a molecular level.

That puts good old British firms like Cambridge Antibody Technologies and Celltech back into the investor spotlight. CAT has a library of almost a trillion antibodies; Celltech is one of Europe's largest biotechs, with a good track record in discovering and developing new drugs.

And it is not just the human genome either.

The Salt Lake City-based gene discovery company Myriad Genetics has sequenced the entire rice genome. That earned it a tidy �37m from the agribusiness giant Syngenta. The only question now is how much Syngenta will earn over the years if it uses this gene information to develop super-rice.