LAWYERS for a US biotechnology company have defended the granting of a controversial patent over a common genetic mutation for breast cancer, rejecting accusations it amounts to the privatisation of the human body.

In the first court case in Australia challenging the practice of granting patents over human genetic material, counsel for Myriad Genetics said the BRCA1 mutation -- for which the company gained a patent in 1994 -- qualified as an invention because the act of removing it from the body changed it "chemically, structurally and functionally".

David Shavin QC told the first day of the hearing in the Federal Court in Sydney yesterday that Myriad Genetics had tested "thousands and thousands" of people nearly 20 years ago to identify the location of the mutation in the genome.

"What's in the isolated nucleic acid (taken out of the body) is not the same thing that's in the cell, and that, I think, is the key issue," Mr Shavin told the court.

The case is being keenly watched by patient groups, cancer doctors, legal experts and MPs because of the controversy over the vexed issue of gene patenting generally, as well as specific concerns relating to breast cancer tests.

In 2008 a Melbourne company that holds the Australian rights for Myriad's BRCA1 mutation patent, Genetic Technologies, wrote to the eight public laboratories that were performing the test, informing them it would be asserting its patent rights and insisting on performing all future tests itself.

The company later backed down, but not before a range of groups such as Cancer Council Australia raised the alarm, triggering a Senate inquiry and a parliamentary bill that sought to ban or limit the effect of such patents.

A US court overturned Myriad's patent in 2010 on the grounds that the mutation was a discovery rather than an invention. But the ruling was reversed by an appeal court last year, and may go to the US Supreme Court.

Patient group Cancer Voices Australia and a breast cancer survivor, 65-year-old Brisbane woman Yvonne D'Arcy, are asking the Federal Court to rule the patent invalid on the grounds that the mutation is not an invention.

Rebecca Gilsenan, principal lawyer representing Cancer Voices, said the key characteristic of the gene mutation relevant to the test -- its ability to code for particular proteins -- was identical inside the body and out.

The case is expected to last between five and eight days.