- ANAHEIM, Calif. (Reuters) - Scientists trying to map all the genes in
creatures ranging from bacteria to humans think they are on the verge of
figuring out how to build an artificial life form from genes.
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- Just as Mary Shelley's doctor Frankenstein
used bits of corpses to make a monster, doctor J. Craig Venter hopes to
salvage DNA from dead bacteria to construct his artificial bug.
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- "Shelley would have loved this,"
Venter laughed when asked about the comparison.
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- Their guinea pig is a tiny bacterium
called Mycoplasma genitalium. It lives in the human genital tract and lungs,
causing no known disease, but has the distinction of having fewer genes
than any other organism mapped so far.
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- While humans have about 80,000 genes,
this bug gets along fine with just 470.
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- That makes it a good model for figuring
out precisely which genes are essential for life, and which ones code for
extra value such as having blue eyes or the ability to resist heat.
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- "We are attempting to understand
what the definition of life is," Venter, of Rockville, Md.-based Celera
Genomics Corporation, told a news conference. "We are trying to understand
what the minimum set of genes is."
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- Not only is Mycoplasma genitalium small
and easy to study, but it has a close relative -- Mycoplasma pneumoniae.
And while M. genitalium has 470 genes, M. pneumoniae has the same 470 genes,
plus 200 extra ones.
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- "So we decided these genes were
not essential to life," Venter, who will explain the project to the
annual meeting of the American Association for the Advancement of Science,
said.
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- Venter's team started working backward
-- cutting out some genes to see if the organism would still function.
They did this using transposons, which are genes that act specifically
to cut up other genes.
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- One by one, they cut out mycoplasma genes
to see which ones the organism could live without.
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- This was harder than it sounds. Organisms
have backup systems. "If you knock out one gene, you don't know if
there is some other gene there that is serving the purpose," Venter
said.
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- "How many genes can call in sick
before you no longer have a living cell?"
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- Nonetheless, they got M. genitalium down
to about 300 essential genes.
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- This could form the basis for trying
to put together an artificial M. genitalium, Venter reckons. Perhaps it
could be built base pair by base pair from the nucleotides that make up
DNA, which in turn makes up the genes.
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- DNA is made up of nucleotides, which
join together in pairs, called base pairs, in ladder-like strands twisted
into a double helix.
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- The nucleotides might come from a "whole
bucket of M. genitalium", Venter said. The cells could be burst open
and the raw genetic material taken out to construct the new bacterium.
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- Even if they could make a new life, Venter's
team still might not understand just what they did, because life is much
more complex than they thought. It had been hoped that after a few organisms
had been sequenced, many genes would arise that every living creature has
in common.
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- After all, everything has many of the
same basic functions -- processing food, respiring, building cell membranes
to keep themselves together.
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- But it turns out that different creatures
use different genes for these same functions.
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- "Fifty percent of the genes in every
genome is new to science and we don't know what they do," Venter said.
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- The same is true even of Mycoplasma's
300 basic genes. "One hundred of these we, as scientists, have no
clue as to what they do. It's very humbling," Venter said.
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- But there are types of genes that are
essential to all life. Venter says three types have been found so far.
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- They govern extremely basic cell processes
involving the transport of potassium, calcium and phosphorus.
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- Before he goes any further, Venter said
he wants advice from experts on ethics and religion. "We are asking
whether it is ethical to synthetically make life," Venter told reporters.
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- "We think this discussion is totally
worthwhile ... because it gets down to the definition of what life is,"
he said.
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- Venter left the nonprofit Institute for
Genomic Research last year to join Norwalk, Connecticut-based Perkin Elmer
Corp. and form Celera. They are using privately developed technology to
sequence, or map, all the human genes.
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