(Reuters)
Updated: 2007-09-04 15:26

WASHINGTON -- The first detailed map of a man's genes shows the genetic code is even more complex than anyone thought. For instance, science still cannot pinpoint what makes a person's eyes blue.

Craig Venter is seen in Washington D.C. during a news conference announcing the public release of the map of the human genetic code in a 2001 file photo. [Reuters]

Initial study of genome entrepreneur Craig Venter's own DNA map shows 4.1 million places where his genetic code is different from the basic "reference" human genome.

This is many more than had been expected, including big differences that extend far beyond the single-letter changes that account for much of the variation seen so far.

"I think the biggest surprise is we are lot more different from one another than we thought," Venter said in a telephone interview.

But there are still some mysteries.

"I found out that I have a high probability of having blue eyes," the blue-eyed Venter said in a telephone interview.

"You can't even tell with 100 percent accuracy if I would have blue eyes, looking at my genetic code," he laughed. "We all thought that would be simple."

The researchers at the J. Craig Venter Institute in Maryland, along with teams at The Hospital for Sick Children in Toronto and the University of California San Diego, analyzed Venter's genetic code to compare it with the rival human genome maps published in 2001 by Venter's private company and the publicly funded Human Genome Project.

Both the 2001 genomes used DNA from several volunteers, pooled and then sequenced.

Writing in the Public Library of Science journal PLoS Biology, the researchers said it would also be useful as a rare exercise to thoroughly examine a single person's genome and compare it to these averages.

DISPELLING FEAR

James Watson, who helped discover the double-helix structure of DNA in 1953, has also had his personal genome sequenced and is offering it to other scientists for study.

Both Venter and Watson have said they wanted to serve as examples to a public often afraid of genetic sequencing, in part for fear of being denied jobs or insurance coverage and in part because of privacy concerns.

One thing the researchers wanted to find was if an individual's risk for disease could be discerned just by looking at his or her genes.

Only for a few illnesses is this a certainty. Huntington's disease is one -- if a person carries the mutated Huntington's gene, he or she will develop the deadly and incurable disease.

But most other diseases are the result of a more complex interaction between genes and environment.

Venter, 61, said his father died at the age of 59 of sudden cardiac arrest.

Venter has versions of three genes believed to lower the risk of heart disease and carries two copies of a gene mutation that raise the risk of a heart attack, the study found.

Venter said he started taking a cholesterol-lowering statin drug years ago, even though his cholesterol levels were below those recommended for taking such medications.

"I don't have to have a 100 percent chance of heart disease to think of taking preventative measures," Venter said.

His mother is 84 and still active, he noted.

"Knowing something doesn't change what's in our genetic code. But knowing things maybe gives us a chance to change what could be part of our genetic destiny," Venter said.

The study is available freely to the public at http://biology.plosjournals.org/perlserv/?request=get-document&d oi=10.1371/journal.pbio.0050254.