X-SciTech

Brave New World

By CBSNews.com staff CBSNews.com staff

February 11, 2001 / 11:41 AM EST / CBS

Scientists have released a humbling genetic map of human beings, reports CBS News Correspondent Lee Cowan.

Before this data was released, most believed it took as many as 100,000 genes to build a human. Now, two separate teams of researchers say humans have less than half that much -- meaning we evolved into the most complex life forms on Earth by using only a few more genes than a worm.

"If we were banking on our human pride being derived from the number of genes we have, it was a pretty black day when the numbers came forward," says Dr. Francis Collins, director of the National Human Genome Research Institute.

Who Are We?

Not Unlike…Worms
The map of the human genetic code reveals the genetic instructions that make us who we are. One of the most surprising findings is that humans have less than double the number of genes as worms.

The genome is the complete list of coded instructions needed to make a person.

Humans have far fewer genes than expected at 30,000 to 40,000, compared to the nematode worm with 18,000 and the fruit fly with 13,000.

The difference between humans and fruit flies or worms is that human genes work differently and we have more control genes.

Hundreds of genes appear to have come from bacteria - one of which is a major pathway for depression.

Most mutations occur in males.

There are six feet of DNA in each of our cells packed into a structure only 0.0004 inches across.

If all of the DNA in the human body were put end to end, it would reach to the sun and back more than 600 times.

The information would fill 200 500-page telephone directories.

Between humans, DNA differs by only 0.2 percent.

Even a mustard weed plant gives us a run for our money in terms of the number of genes we have. The difference is what we do with them.

"It looks as if these genes that humans have are particularly clever. They're capable of multitasking. They can do a lot packed into one strand of DNA," says Collins.

Dr. Eric Lander, who heads the Whitehead Institute at MIT were much of the research for the human genome project took place, tells CBS News Early Show co-anchor Jane Clayson that the knowledge could be used to discriminate against people who are genetically prone to disease or other traits.

"I think there are a number of issues there thaare potentially troubling. The extreme would be that we try to reshape the human genetic code and someone's image," he says.

Landler advocates a moratorium on that type of research and new laws to protect people's privacy.

It's hoped that the pair of landmark studies offering the first detailed look at the human genetic code will reveal new leads for finding roots of disease and new understanding of the origin of most inherited genetic mutations.

The analyses were performed by the two teams that made headlines last year for determining nearly all the "letters" of the human DNA code. That three-billion letter code, called the genome, is a chemical sequence that contains the basic information for building and running a human body.

The genome work is expected to help scientists find disease-promoting genes, tailor therapies to particular patients, evaluate environmental hazards and study human evolution and migration.

But the biggest initial impact is expected to be on drug development, customizing drugs to individual genetic profiles and earlier diagnosis of disease.

Currently, there are fewer than 500 targets for all the drugs on the market. Scientists predict the sequencing will increase that number to several thousand, sparking a boom in gene research in the pharmaceutical industry.

"There are potentially a huge number of targets that can be investigated for potential drugs. There is also the personalization of medicine," says Tim Hubbard of the Sanger Centre in Cambridge, England who worked on the project.

The two teams, which worked independently, estimated roughly the same number of human genes: about 26,000 to 39,000 according to Celera, and about 30,000 to 40,000 according to the consortium. Scientists with both groups said the best bet is something fewer than 35,000.

While the result agrees with some recent estimates, it's in the lower range of what scientists have thought. Some researchers put the count above 100,000 genes.

The new estimates are fairly close to the 25,000 genes in the small flowering plant called Arabidopsis thaliana, the 19,000 genes in the tiny worm C. elegans, or the 13,600 genes in the fruitfly Drosophila.

So why are humans so much more complex than a fruit fly or worm? That remains a mystery. But scientists stress that the sheer number of genes is only a starting point for creating complexity.

Most genes exert their effects by telling the body make certain proteins, and human genes are more likely than fly or worm genes to give rise to multiple proteins rather than just one. What's more, human proteins are more versatile, scientists say.

And the timing of when genes turn on and off, and in what tissues they are active, can also make a big difference in their effect.

Both groups also say their data have already helped scientists find genes that promote disease. The consortium's paper lists about 30 such genes found with the help of its data, and J. Crag Venter, president of Celera, says his group's database has led to finding of such genes as well.

Venter recalled that he had spent 10 years trying to find a particular gene, a task "that now can be done with a 15-second computer search." So scientists can quickly focus on studying a new gene rather than having to spend lots of time tracking it down, he said.

The consortium also confirmed a recent finding that men's bodies create inheritable mutations at about twice the rate of women's. Prior estimates had suggested the disparity was even greater.

The gender difference is a mixed message for men: It suggests they provide the greater force for evolutionary change, but also that they create more glitches that may promote disease.

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