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
http://www.nature.com/nsu/040329/040329-7.html

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.

http://www.nature.com/nsu/040329/040329-11.html

The Rat Genome can be found at
http://www.nature.com/nsu/rat/

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.

http://www.nature.com/nsu/040329/040329-5.html

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.
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