US Supreme Court judges have signalled a reluctance to issue too broad a ruling about patents on human genes.

The court heard arguments on Monday in a case that could profoundly reshape US medical research and the fight against diseases, with nearly 20 percent of about 24,000 human genes under patent, some linked to cancer and Alzheimer's disease.

The US Patent and Trademark Office has awarded patents on human genes for almost 30 years, but opponents of Myriad Genetics' patents on two genes linked to increased risk of breast and ovarian cancer say patent protection should not be given to something that can be found inside the human body.

The company says patents for the two genes, awarded in 1998, have helped it raise the money "necessary to decode the genes, design and deliver the tests, interpret the results, and help patients," to the benefit of a million people.

Critics accuse Myriad of barring research by other institutions on the BRCA genes and making the test too expensive for many patients, with a cost of  $3,000 to $4,000.

Several Supreme Court judges, including Justice Elena Kagan, expressed concern at Myriad's argument that without the ability to recoup its investment through the profits that patents bring, breakthrough scientific discoveries needed to combat all kind of medical illnesses would not happen.

'Insufficient' statement

``Why shouldn't we worry that Myriad or companies like it will just say, `Well, you know, we're not going to do this work any more?''' Kagan said.

Lawyer Christopher Hansen said that a company could get recognition for its work and that money for research would always be available, a statement that Justice Anthony Kennedy said insufficient.

``I don't think we can decide the case on, `Don't worry about investment, it'll come,''' Kennedy said.

But the justices also appeared to be inclined to draw a line between synthetically produced genetic material and natural

A court ruling along those lines, suggested by the Obama administration, would have less impact on Myriad. Some of the latest research using human genes involves a synthetic form of DNA called recombinant DNA, or rDNA.

The Supreme Court has said that abstract ideas, natural phenomena and laws of nature cannot be given a patent, which gives an inventor the right to prevent others from making, using or selling a novel device, process or application.

Myriad has used its patents to develop its BRACAnalysis test looks for mutations on the breast cancer predisposition gene, or BRCA.

Those mutations are associated with much greater risks of breast and ovarian cancer. Men can carry a BRCA mutation, raising their risk of prostate, pancreatic and other types of cancer.

Myriad sells the only BRCA gene test.

Source: Agencies