Evolved DNA stitches itself up Could DNA have kick-started
life on Earth instead of RNA? 31 March 2004 PHILIP BALL
Researchers have managed to create bits of DNA that can
stitch themselves together without a helping hand from other
molecules. By contrast, natural DNA needs enzymes to stitch
itself up, correct mutations, or make copies of itself.
The creation of this super-capable DNA suggests that rare
bits of natural DNA might have evolved the same
capability in the past. That could alter our thinking
about how life began.
Researchers have known for decades that RNA, the molecule
that translates information in DNA into proteins, can show
enzyme-like behaviour. These special forms of RNA, called
ribozymes, won their discoverers a Nobel Prize in the 1980s.
Since then, several ribozymes have been found in cells.
Ronald Breaker of Yale University and his colleagues have
shown that the equivalent molecules for DNA, deoxyribozymes,
can be created. "We have shown that RNA is not special in
that regard," says Breaker.
Now they have gone one step further, devising deoxyribozymes
that catalyze links between DNA molecules themselves, as
they report in the Journal of the American Chemical
Society1. Creation of these links is an essential part of
the process by which DNA replicates itself.
If natural DNA could do that too, it might have been able to
kick-start life on this planet.
Many researchers reckon that RNA, rather than DNA, formed
the first building block of life, in part because it has
this capacity to behave like an enzyme. There are many other
pieces of evidence to indicate that life on our planet began
with RNA, but it now seems that this molecule's priority may
owe more to chance than to any special capabilities.
"If you play out the origin of life on a thousand different
planets like Earth it may sometimes look very different,"
says Breaker, suggesting our world might begin with DNA
rather than RNA.
Read the rest at Nature nature.com040329Open ↗
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Rat genome unveiled Deciphered DNA will boost medical
research. 1 April 2004 HELEN R. PILCHER
The humble lab rat is the latest to spill its genetic
secrets. The Brown Norway rat (Rattus norvegicus) is the
third mammal to have its genome sequenced, joining mouse and
man. The information should help medical research and
further our understanding of evolution.
The sequence will further raise the rat's high-profile in
medical research. Over the last century, the rat's image has
transformed from plague carrier to indispensable tool in
experimental medicine and drug development (see Rat Roll of
honour). It is the animal of choice for studying physiology
and pharmacology, and is used in fields ranging from
cardiovascular disease to space motion sickness.
"The rat is used to mimic just about every aspect of every
disease known to man," says pharmacologist John Fozard
from Novartis in Basel, Switzerland. Knowing its genetic
make-up will help researchers find disease-related genes,
and further tease apart how genes and the environment
affect health.
The sequence, revealed in Nature1, has about 25,000 genes.
Around 90% of these have matches in the mouse and man. This
means that almost all of the known disease-related human
genes have counterparts in the rat, says Richard Gibbs from
Baylor College of Medicine, Houston, Texas, who led the
collaborative Rat Genome Sequencing Consortium. By tweaking
these, researchers should be able to make better rat models
of disease.
It will also aid drug discovery, says Gibbs. Rats are widely
used to test drug efficacy and safety. Knowledge of their
genome should throw up new targets for drug intervention.
"You cannot over emphasize the importance of having a
complete database like this," he adds.
nature.com040329 11.htmlOpen ↗
The Rat Genome can be found at
nature.comratOpen ↗
Comment: A copy of the rat's genome makes a great
Birthday/Christmas gift for that truly erudite pet rat.
Methane found on Mars Volcanoes likely source of gas. 30
March 2004 PHILIP BALL
Methane has been spotted in the atmosphere of Mars by
several researchers, reigniting speculations about the
possibility of life on the red planet.
On Earth, methane is a common by-product of the
metabolism of single-celled organisms. So its presence in
the martian atmosphere could be a sign of bacteria still
living on the planet.
But that isn't the only possible explanation, says Vittorio
Formisano of the Institute of Physics of Interplanetary
Space in Rome, who helped to confirm the finding. The
methane could be produced by purely geological processes,
such as volcanic activity.
The gas was first seen on Mars by a team of astronomers led
by Michael Mumma of NASA's Goddard Space Flight Center in
Maryland. They used Earth-based telescopes to detect gaps in
the spectrum of infrared light coming from Mars. These gaps
occur at wavelengths where methane absorbs radiation.
The findings have now been confirmed by Mars Express, the
European Space Agency craft that released the ill-fated
Beagle 2 lander at Christmas.
Comment: It's amazing how we can probe a planet thousands of
kilometres away and find traces of invisibly small microbes,
but can't find thousands of litres of toxic chemicals in
Iraq. I guess that is the difference between a
scientifically generated hypothesis, and a politically one.
But "C average" presidents are hardly expected to understand
anything remotely scientific, are they?
Posted by Robert Karl Stonjek.