The Senate passed earlier versions of the bill twice before, but they were blocked from coming up for House floor votes. This year, the House passed it by a bipartisan landslide, but Coburn has held up the legislation in the Senate, saying it could place too much strain on businesses.

"We're not really clear on what Coburn wants, because his excuses don't make sense," said the bill's original sponsor, Rep. Louise Slaughter (D-New York). "But if this bill got to a floor vote in the Senate, I think it'd pass almost unanimously."

Coburn spokesman John Hart said his boss supports the intent of the Genetic Information Nondiscrimination Act, known as GINA. Coburn voted for a nearly identical bill in 2005, but now says the bill's language exposes employers to too much liability. Supporters of the bill see Coburn's new beef as another in a string of inconsequential objections to the legislation.

23andMe, Navigenics and Decode Genetics have recently launched programs to scan individual's genomes and provide access to the information online. Customers will have to spend a for 23andMe's service.

In the absence of federal legislation, most states provide some degree of protection against discrimination. Many have gone further, explicitly providing genetic-privacy protections. Alaskan law (.pdf), for example, says DNA samples are an individual's private property. Still, companies offering personal genome scans, as well as biotechs offering genetic diagnostic tests, worry that their businesses will not gain traction without a federal law.

Slaughter introduced GINA in the House 12 years ago, but Republican leadership repeatedly blocked a vote, even as it passed the Senate twice. Under this year's new Democratic majority, the House passed GINA, 420-3 (H.R. 493), and it appeared ready to sail through the Senate (S. 358). But Coburn, exercising a prerogative available to all senators, placed it on hold, which requires a supermajority of 60 senators just to bring the bill up for a relatively rare floor debate.

An internal memo obtained Thursday from Coburn's office said the senator's make-or-break objection was the possibility that an employer who provides health insurance for its workers could be sued both as an insurer and as an employer. That means employers could be hit for much higher damages than insurers.

Representative Slaughter said she'd never heard that particular objection from any company in 12 years of campaigning on behalf of GINA. "But it's pretty creative," she said.

Coburn is a physician. He picked up the nickname "Dr. No" from pundit George Will, because of his frequent contrarian positions and use of the hold prerogative. Coburn has consistently opposed bills that enable lawsuits against businesses and his fellow medical doctors.

The U.S. Chamber of Commerce and trade associations like the National Retail Federation are GINA's main opponents, claiming it would spur frivolous lawsuits.

Michael Eastman, executive director of labor policy at the U.S. Chamber of Commerce, applauded the Senator's move to stop the bill.

"Coburn has been willing to put his name out there," he said.