Analysis shows it's proteins not genes that count
By Maggie Fox, Health and Science Correspondent
WASHINGTON, Feb 11 (Reuters) - Our future may not lie in
our genes, after all.
Two separate teams of researchers will report on Monday
that they have taken the first in-depth look at the human
genetic code and found about half what they expected to find.
Instead of 60,000 to 80,000 genes, we have only 30,000 to
40,000.
Both teams agree this means that, in humans anyway, it is
proteins that matter -- much more so than genes.
"Those who are looking for forgiveness of responsibility
for their own lives in the genetic code will be very
disappointed," Craig Venter, president and chief scientific
officer of Celera Genomics Inc. <CRA.N>, the private company
that did one of the studies, said in a telephone interview.
The human body, it seems, is set up to adapt to its
environment, by cutting up and recombining the protein
"products" of genes to make a protein suitable for the
circumstance.
Each gene makes one protein -- this is the basic function
of any cell. Researchers had known that proteins often have to
be sliced in a certain way, a process known as cleaving, before
they do anything useful.
"Most of biology happens at the protein level, not the DNA
level," Venter said.
What had not been known was the degree to which this is
true. The implications could be profound for medical science,
which had hoped to find easy genetic answers to disease and to
how people will respond to drugs.
GENE PATENTS "IRRELEVANT"
"This shows how irrelevant human gene patents are," Venter
said. "The drug industry has been saying 'one gene, one patent,
one drug'. But the uses for this approach can be counted on
fingers."
Both teams, who publish their findings in the rival
scientific journals Nature and Science, are fairly certain.
"Given all the tools that we threw at this problem, we
cannot imagine that there are many more genes," Mark Adams,
vice president at Celera, told a briefing for journalists.
"We only have twice as many genes as a fruit fly. But we
are more complex. We can think more thoughts. Our bodies can do
more things."
Humans have 3.1 billion base pairs of genetic code. A base
pair is a joining of two nucleotides -- known by the letters
A,C,T and G. These repeat over and over in various combinations
to make amino acids, which in turn combine to make proteins.
"The size of the genome, the number of base pairs, is
irrelevant to biology," Venter said.
"Corn has the same number of genes as humans. The lily
plant has 91 billion pairs of genetic code."
Each protein equals a gene, but there are long stretches of
base pairs that do not code for proteins, areas once known as
junk DNA. These areas may help control genes.
Only just over one percent of the genome is accounted for
by protein-expressing genes. Venter says all this means genes,
per se, are just a small part of the story.
"Genes don't determine whether you get colon cancer," he
said. "They determine whether you have an increased risk for
colon cancer. We get a set of probabilities from our genetic
code, a sort of range of parameters that we can work within."
KIND OF HUMBLING
"It's kind of humbling, isn't it?" Ari Patrinos of the U.S.
Department of Energy, which funded much of the public effort,
said in a telephone interview.
"There are very, very few few traits or diseases that are
monogenic (caused by a single gene). It's been an emerging
consciousness over the past five years, and the recognition
that ... our genes don't control everything."
It also means the so-called "junk DNA" may be more
important than at first thought.
"We just don't know. We don't call it junk," Venter said.
Eric Lander, who heads the genome lab at Massachusetts
Institute of Technology's Whitehead Institute, said the
"alleged junk" provides a history.
"The junk is amazing. Every piece of junk in the genome
represents a transposable element," he said.
In other words, it is genetic material that people got from
elsewhere, such as from bacteria the readily lend their DNA
out, retroviruses that inject their genetic information into
cells, or by a cut-and-paste process done by genetic elements
known as transposons. If it stayed there through generations,
it might do something useful.
Lander thinks some of the "junk" may help regulate genes --
a role that is more important the fewer genes there are.
And some of the genes are borrowed, too. Lander said his
team found that the gene for monoamine oxidase, an enzyme
implicated in depression and targeted by drugs called MAO
inhibitors, came from bacteria.
NOT EVERYONE AGREES
Not everyone agrees with all the conclusions.
"We know that they have missed very, very many genes that
we know exist," William Haseltine, head of Rockville,
Maryland-based Human Genome Sciences Inc. <HGSI.O>, said in a
telephone interview.
"They have missed at least half the genes, maybe more,"
added Haseltine, whose company holds more than 100 gene
patents. "They have no medical discovery and they only found a
third of the genes. That's a bore."
Haseltine, whose company looks for "expressed" genes --
those that actually make a protein -- by using bits of DNA
called expressed sequence tags (ESTs), says he believes there
are 120,000 human genes.
Another company that says it has explored the genome, Palo
Alto, California-based Incyte Pharmaceuticals Inc.<INCY.O>,
maintains there are 140,000.
(( -- Washington newsroom 202 898 8300, fax 202 898 8383,
e-mail washington.bureau.newsroom@reuters.com))
REUTERS
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