The "right" to know about one's health has dominated discussions about the ethics of genetic screening, a conference will hear tomorrow. But the "right not to know" has received little attention, says Ruth Chadwick, of the Centre for Professional Ethics at the University of Central Lancashire.

Similarly, the concept of a "duty to know" about one's genetic make-up needs more discussion, says Professor Chadwick. Potential parents, for example, may have a duty rather than a right to discover whether they may pass a serious disease on to their offspring, so that they can make a responsible reproductive decision.

Professor Chadwick will address the second annual meeting of academics involved in Euroscreen, a three-year European project to assess the ethics of genetic screening, in York tomorrow.

She said: "A lot of discussion has been about the right of the patient to get information but it is always assumed that it is a good thing to know. Genetics is different from other kinds of medical information. If you don't want to know something else then you can choose not to consult a medical practitioner."

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Genetic information can seep through because it can apply to all members of your family.

The issue becomes crucial for a parent deciding whether or not to tell a child that it may develop a disease in later life, she said.

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Once people feel they have a right not to know about their genes they could demand moratoria on certain types of genetic research, according to Darren Shickle, public health physician at the University of Wales, who will also address the conference.

"I'm concerned about the subtle pressures that are placed on people when they enter screening programmes," he said. "A lot of harm can come from screening and once the technology becomes available it is very difficult for people to resist the pressure to know."

If a health authority offers a test despite the fact that resources are scarce, for example, there is pressure to be screened, he said.

Such pressures could suddenly appear in the areas of intelligence, aggression or homosexuality, if research is allowed to continue, he said.

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A United States scientist said this week, for example, that he has found further evidence that homosexuality in men is partly genetic.

The Euroscreen group will produce recommendations at the end of its third year.