Scientists sequence first human chromosome

December 1, 1999
Web posted at: 3:33 p.m. EST (2033 GMT)

(CNN) -- As the century draws to a close, scientists say a new book is being written that will change the way we see ourselves. It starts with the inaugural results of the Human Genome Project, which has sequenced the first human chromosome.

The achievement, made by a group of scientists from England, the United States, Canada, Sweden and Japan, is published in the journal Nature. It is an important step forward for the $3 billion Human Genome Project, which is working to detail the tens of thousands of genes in humans.

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CNN's Rhonda Rowland reports on the first human chromosome decoded. QuickTime Play Real 28K 80K Windows Media 28K 80K

Researchers were able to find only 97 percent of the chromosome's genetic material, but the results are considered complete for now.

"For the first time we can see the entire landscape of a human chromosome, the basic unit of human inheritance, how the genes are organized, how they're laid out on the chromosome," said Dr. Francis Collins, chair of the National Human Genome Research Institute.

"I think this is probably the most important scientific effort that mankind has ever mounted," he said. "That includes splitting the atom and going to the moon."

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Select a term: base pair cell chromosome DNA sequencing DNA (deoxyribonucleic acid) gene genetic code genome mutation nucleus protein Source: National Human Genome Research Institute

The human genetic pattern, or genome, is a biological map laying out the sequence of 3 billion pairs of chemicals that make up the DNA in each cell. All human DNA is contained within 23 pairs of chromosomes.

In the center of any normal human cell there are 46 X-shaped chromosomes. Within each chromosome is bundled a double-stranded helix of DNA. That is where human genes reside. These genes carry instructions for everything from hair color and height to how the brain is organized.

More than 30 human disorders are already associated with changes to genes of chromosome 22. These include a form of leukemia, disorders of fetal development and the nervous system, and schizophrenia.

Already researchers are testing gene therapies to correct misfirings and to make cells work correctly. Scientists hope these therapies may one day be reliable enough to treat diseases without the sometimes debilitating side effects of some drugs.

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This milestone is by no means the end of research, scientists say.

"What happens now is a whole host of fascinating experimental challenges to figure out. What do these genes do individually, and how do they work together to do all the things we humans are capable of?" said Collins.

Researchers will also look at how differences in our individual genomes lead to the development of disease or protect against particular disorders.

"The first benefit will be diagnosis: in other words, the identification, particularly the early identification, of disease."

Scientists expect the decoding of the rest of the chromosomes to come quickly. The next one may be No. 7.

"One down, the others to go," said Ian Dunham, a biochemist with the Sanger Center in Cambridge, England, and lead author of the Nature report. "It's a great relief to have it (chromosome 22) finished."

Scientists expect to have sequenced the other chromosomes by next spring, a milestone they say is hard to overemphasize.

Medical Correspondent Rhonda Rowland and The Associated Press contributed to this report.