WASHINGTON — President Bush yesterday signed legislation to protect people from losing their jobs or health insurance when genetic testing reveals they are susceptible to costly diseases.

Broadly embraced in Congress, the anti-discrimination measure aims to ensure that advances in DNA testing won’t end up being used against people.

The new law forbids employers and insurance companies from denying employment, promotions, or health coverage to people when genetic tests show they have a predisposition to cancer, heart disease, or other ailments.

Mr. Bush praised the bill for protecting “our citizens from having genetic information misused.”

Sponsors of the legislation call it a groundbreaking protection of civil rights. About a dozen of them gathered in the Oval Office as Bush signed the bill, but not Senator Kennedy, to whom the president paid particular tribute.

Mr. Kennedy, who learned this week that he has a malignant brain tumor, has called the genetic anti-discrimination bill “the first major new civil rights bill of the new century.” The Democratic senator from Massachusetts left the hospital yesterday.

“All of us are so pleased that Senator Kennedy has gone home, and our thoughts and prayers are with him and his family,” Mr. Bush said. People today have far more information about their hereditary disposition to afflictions. Bill sponsors said that has increased the likelihood that insurers or employers might deny people work or insurance to avoid risks.

“This is a tremendous victory for every American not born with perfect genes — which means it’s a victory for every single one of us,” Rep. Louise Slaughter of New York, one of the bill’s key sponsors, said. “Since all of us are predisposed to at least a few genetic-based disorders, we are all potential victims of genetic discrimination.”