- (Reuters) For the first time, scientists have mapped
virtually an entire human chromosome, one of the chains of molecules that
bear the genetic recipe for human life.
- Senior research fellow at the Sanger Center, Dr. Ian
Dunham, makes his presentation on Chromosome 22, the complete genetic code
of a human chromosome Wednesday. (AFP Photo)
- The achievement announced Wednesday is an important step
for the $3 billion Human Genome Project, which is attempting to detail
the tens of thousands of genes that carry instructions for everything in
a human -- from brain function to hair color to foot size.
- "This is the first time that we've had a complete
chapter in the human instruction book, and that's pretty amazing,"
said Francis Collins, who chairs the international project from the National
Institutes of Health.
- "I think this is probably the most important scientific
effort that mankind has ever mounted. That includes splitting the atom
and going to the moon," he said.
- In laying out the chemical instructions for life, scientists
believe they are in the early stages of revolutionizing the study of human
development and medicine.
- Already, researchers have begun testing several biological
therapies that replace faulty genes or correct their misfirings to make
cells work correctly. Such therapies, if they can be made reliable, would
bring a more precise way to treat diseases without the sometimes debilitating
side effects of conventional drugs.
- A draft of the entire genome was expected to be done
next spring, but the milestone announced Wednesday may hasten its completion.
The study's details appear in the journal Nature.
- 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.
- What the scientists have done is lay out the order of
about 545 of the estimated 700 genes on chromosome 22, which has about
1.1 percent of the genes in the human body.
- About 55 percent of the genes were new to researchers
during the study; 45 percent already had been discovered during the Human
- The chromosome 22 group, which includes British, American,
Japanese, Canadian and Swedish scientists, could find only 97 percent of
the chromosome's genetic material. Scientists said technological limits
prevented them from analyzing the remaining 3 percent, which could have
as many as 200 genes.
- While five government-supported centers and many university
labs have already identified about a third of the whole genome, the map
of chromosome 22 is the most complete part so far.
- "One down, the others to go," said Ian Dunham,
a biochemist with the Sanger Centre in Cambridge, England, and lead author
of the Nature report. "It's a great relief to have it finished."
- Genes are arrayed along chromosomes, the rod-shaped bodies
inside the nucleus of a cell. Proteins and other compounds carry out the
instructions of genes.
- Inside the chromosomes, genetic material is linked along
tightly coiled strands of the master molecule DNA, which twists like a
spiral ladder. Each rung is built with pairs of four chemical bases ordered
in different numbers and combinations to form genes.
- Chromosome 22 is the second-smallest of the 23 pairs.
Scientists took aim at the tiny target because its genes are densely packed
and very active in a variety of diseases.
- Mutations to genes along chromosome 22 contribute to
heart defects, immune system disorders, cancers, schizophrenia and mental
- Researchers cautioned that mapping a gene is only an
early step in understanding the gene's function and how it might contribute
to a particular disease.
- "Biologists trying to understand, diagnose, treat
and eventually cure human genetic disease will be empowered by our data,"
said Richard K. Wilson of the Washington University School of Medicine
in St. Louis.
- The Human Genome Project isn't the only effort to describe
the genetic code. The government project is competing with a privately
funded effort by Rockville, Md.-based Celera Genomics, whose work is scheduled
for completion by the end of 2001.