Companies holding more than 40,000 patents on DNA molecules have essentially staked claim to the entire human genome for profit, U.S. researchers say.

Medical researcher Christopher E. Mason of Weill Cornell Medical College in New York says an analysis of patents held on human DNA raises concerns.

"If these patents are enforced, our genomic liberty is lost," he said. "Just as we enter the era of personalized medicine, we are ironically living in the most restrictive age of genomics. You have to ask, how is it possible that my doctor cannot look at my DNA without being concerned about patent infringement?"

Mason and Jeffrey Rosenfeld of the University of Medicine and Dentistry of New Jersey said 41 percent of the human genome is covered by DNA patents that often cover whole genes.

They also said that, because many genes share similar sequences within their genetic structure, if all of the "short sequence" patents were allowed in aggregate, they could account for 100 percent of the genome, the study published in Genome Medicine said.

Under U.S. patent law, researchers who are first to find a gene that promises a useful application, such as for a diagnostic test, can patent those genes.

Patients and doctors wishing to perform such a diagnostic test would have to utilize the expensive services of the patent owner even though "hundreds of clinical laboratories around the country could perform such a test for possibly much less," Mason said.

The U.S. Supreme Court is expected to review genomic patent rights in a hearing on April 15.

"I am extremely pro-patent but I simply believe that people should not be able to patent a product of nature," Mason said.

"Moreover, I believe that individuals have an innate right to their own genome, or to allow their doctor to look at that genome, just like the lungs or kidneys. Failure to resolve these ambiguities perpetuates a direct threat to genomic liberty, or the right to one's own DNA."