Today, the European Patent Office in Munich will hear the final arguments about patenting a mouse - the "Harvard Oncomouse" - which has been genetically engineered to develop cancer. Meanwhile, earlier this week, it became clear that the US government has patented the genes of a tribesman from Papua New Guinea.

These cases are landmarks for humanity's attitude to itself and the rest of the living world. It would be difficult to come up with less appealing standard-bearers than Oncomouse and PNG man for the brave new world of genetic engineering.

In 1984, scientists at the Harvard Medical School stitched "oncogenes" - genes known to provoke the development of cancer - into the DNA of laboratory mice. At first, the university's application to patent its "invention" was turned down: the European Patent Office ruled that animals are naturally occurring life forms which cannot be classed as inventions and so cannot be patented. But Harvard pursued its claim aggressively and in 1992 the EPO granted the Harvard Oncomouse a patent, sparking protest from groups across Europe. Today's appeal will determine whether the patent is confirmed or withdrawn.

This is not a straightforward question of animal welfare. Nearly 3 million animal experiments were performed in British laboratories last year, some of them involving suffering comparable with or exceeding that endured by the oncomouse. Most of us can accept, albeit with discomfort, the necessity of such work. Few parents would put shampoo on their baby's hair without knowing that its low toxicity had already been proved.

But the commercial exploitation of animal suffering is different. That a great American university - which ought to be the seat of liberal and enlightened values - should be interested in making a fast buck out of marketing an animal predetermined to develop painful tumours indicates that something has gone far wrong with our calculus of moral standards.

The implication is also troubling that, by granting a patent, society can regard a living animal as an invention - a biochemical automaton which humanity can reprogramme as it wishes. Any biologist will tell you that there is little difference between a mouse and a man - if we regard animals as automata, can we avoid coming to the same conclusions about ourselves? The patenting of DNA from a man in Papua New Guinea, who enjoys a rare immunity to leukaemia, reinforces that concern.

The international biotechnology industry must, if only in its own interest, reassure us that genetic engineers are sensitive to public concerns as they exercise their new technical powers to alter DNA. The oncomouse case sends all the wrong signals. Not even Frankenstein tried to patent his creation.