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Did soggy space rocks give life left-hand bias?
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DNA shape could The snap, crackle and pop of an alien world be clue to function ALIEN worlds that are friendly to to doubt the idea’s feasibility. Because a magnetic field helps
RUSSELL KIGHTLEY/SPL
life could reveal themselves by radio signals crackling from their magnetic fields. When struck by high energy particles in the solar wind, an exoplanet’s magnetic field may produce radio signals from auroras in the planet’s atmosphere. While current telescopes have yet to pick up these crackles, it’s an area worth exploring, argue Joseph Lazio at the Naval Research Laboratory in Washington DC and colleagues in a paper submitted to Astro2010.
to preserve atmospheres and oceans, a magnetosphere may signify that a planet has complex surface life. “This is something we think is worth studying at a modest level,” says Lazio, “the payoff could be immense.” The snag is that we would need a space telescope 100 times as sensitive as any planned to find auroras within a few dozen light years, because the Earth’s atmosphere would absorb the low frequency signals. That leads some planet hunters
We have never directly detected the magnetosphere from any extrasolar planet, despite strong efforts, says Geoff Marcy of the University of California, Berkeley. Yet planetary magnetospheres would be easier to spot at radio frequencies than planets themselves, says Gordon Walker of the University of Victoria in British Columbia, who has spotted an exoplanet’s magnetic field indirectly by studying its host star. “It’s an exciting proposal,” he says. TONY HALLAS/SCIENCE FACTION/CORBIS
THE twists and bumps on stretches of non-coding DNA could give clues to what they are there for. The DNA that codes for proteins makes up only 2 per cent of the human genome. Other functions, such as switching on genes, are embedded somewhere in the remaining 98 per cent. One way to home in on the functional areas is to scan for sequences that humans share with other mammals, suggesting they have been conserved for a reason. But Thomas Tullius of Boston University and his colleagues wondered whether different sequences might show up if they looked instead at the DNA’s outward shape. DNA’s complex chemistry means two similar sequences can produce very different outer shapes, while two different sequences can have similar shapes. The team used a computer program to predict the outer shape of a genome from its base pairs. When they compared the shape of the human genome with the genomes of 36 other mammals, 50 per cent more DNA appeared conserved than if they just took account of sequence (Science, DOI: 10.1126/science.1169050). Shape could indicate function because it helps determine whether proteins can bind to and activate a stretch of DNA, says Tullius.
One gene good, two genes bad WHERE protection against Alzheimer’s is concerned, you can have too much of a good thing. If you inherit one copy of a particular gene mutation it seems to protect you from Alzheimer’s. With a copy from each parent, you may be in trouble. Fabrizio Tagliavini of the Carlo Besta National Neurological Institute in Milan, Italy, and colleagues discovered the mutation in a 44-year-old man with signs of early-onset Alzheimer’s who didn’t have the usual gene mutations. Both he and a younger sister with mild cognitive problems, have two copies of a mutation in a gene called APP, while relatives with just one copy of the mutation, including an 88-year-old aunt, seemed to be actively protected against the disease (Science, DOI: 10.1126/ science.1168979). APP makes the protein A-beta, which can form clumps in the brain, blocking neurons from firing. But experiments showed that a mix of normal and mutant A-beta is less likely to clump than mutant protein or normal protein alone, which may explain why one copy of APP is protective.
Soggy space rocks and left-handed life WET rocks hurtling around the solar system may have given life on Earth its addiction to left-handed building blocks. Almost all life on Earth uses left-handed amino acid molecules instead of their right-handed counterparts. In the 1990s, scientists found that meteorites contain up to 15 per cent more of the lefthanded versions too. So space rocks bombarding the early Earth may have biased the planet’s chemistry. A linked theory has it that polarised starlight can preferentially destroy righthanded amino acids on asteroids,
though this alone cannot explain the strength of the bias on meteorites. Now Daniel Glavin and Jason Dworkin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have shown that water amplifies the bias. They studied an amino acid called isovaline in six meteorites that showed ancient evidence of 1000 to 10,000 years’ exposure to liquid water. The longer water persisted in the rock, the stronger its left-handed isovaline bias, the pair found (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0811618106).
21 March 2009 | NewScientist | 13
DNA shape could The snap, crackle and pop of an alien world be clue to function ALIEN worlds that are friendly to to doubt the idea’s feasibility. Because a magnetic field helps
RUSSELL KIGHTLEY/SPL
life could reveal themselves by radio signals crackling from their magnetic fields. When struck by high energy particles in the solar wind, an exoplanet’s magnetic field may produce radio signals from auroras in the planet’s atmosphere. While current telescopes have yet to pick up these crackles, it’s an area worth exploring, argue Joseph Lazio at the Naval Research Laboratory in Washington DC and colleagues in a paper submitted to Astro2010.
to preserve atmospheres and oceans, a magnetosphere may signify that a planet has complex surface life. “This is something we think is worth studying at a modest level,” says Lazio, “the payoff could be immense.” The snag is that we would need a space telescope 100 times as sensitive as any planned to find auroras within a few dozen light years, because the Earth’s atmosphere would absorb the low frequency signals. That leads some planet hunters
We have never directly detected the magnetosphere from any extrasolar planet, despite strong efforts, says Geoff Marcy of the University of California, Berkeley. Yet planetary magnetospheres would be easier to spot at radio frequencies than planets themselves, says Gordon Walker of the University of Victoria in British Columbia, who has spotted an exoplanet’s magnetic field indirectly by studying its host star. “It’s an exciting proposal,” he says. TONY HALLAS/SCIENCE FACTION/CORBIS
THE twists and bumps on stretches of non-coding DNA could give clues to what they are there for. The DNA that codes for proteins makes up only 2 per cent of the human genome. Other functions, such as switching on genes, are embedded somewhere in the remaining 98 per cent. One way to home in on the functional areas is to scan for sequences that humans share with other mammals, suggesting they have been conserved for a reason. But Thomas Tullius of Boston University and his colleagues wondered whether different sequences might show up if they looked instead at the DNA’s outward shape. DNA’s complex chemistry means two similar sequences can produce very different outer shapes, while two different sequences can have similar shapes. The team used a computer program to predict the outer shape of a genome from its base pairs. When they compared the shape of the human genome with the genomes of 36 other mammals, 50 per cent more DNA appeared conserved than if they just took account of sequence (Science, DOI: 10.1126/science.1169050). Shape could indicate function because it helps determine whether proteins can bind to and activate a stretch of DNA, says Tullius.
One gene good, two genes bad WHERE protection against Alzheimer’s is concerned, you can have too much of a good thing. If you inherit one copy of a particular gene mutation it seems to protect you from Alzheimer’s. With a copy from each parent, you may be in trouble. Fabrizio Tagliavini of the Carlo Besta National Neurological Institute in Milan, Italy, and colleagues discovered the mutation in a 44-year-old man with signs of early-onset Alzheimer’s who didn’t have the usual gene mutations. Both he and a younger sister with mild cognitive problems, have two copies of a mutation in a gene called APP, while relatives with just one copy of the mutation, including an 88-year-old aunt, seemed to be actively protected against the disease (Science, DOI: 10.1126/ science.1168979). APP makes the protein A-beta, which can form clumps in the brain, blocking neurons from firing. But experiments showed that a mix of normal and mutant A-beta is less likely to clump than mutant protein or normal protein alone, which may explain why one copy of APP is protective.
Soggy space rocks and left-handed life WET rocks hurtling around the solar system may have given life on Earth its addiction to left-handed building blocks. Almost all life on Earth uses left-handed amino acid molecules instead of their right-handed counterparts. In the 1990s, scientists found that meteorites contain up to 15 per cent more of the lefthanded versions too. So space rocks bombarding the early Earth may have biased the planet’s chemistry. A linked theory has it that polarised starlight can preferentially destroy righthanded amino acids on asteroids,
though this alone cannot explain the strength of the bias on meteorites. Now Daniel Glavin and Jason Dworkin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have shown that water amplifies the bias. They studied an amino acid called isovaline in six meteorites that showed ancient evidence of 1000 to 10,000 years’ exposure to liquid water. The longer water persisted in the rock, the stronger its left-handed isovaline bias, the pair found (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0811618106).
21 March 2009 | NewScientist | 13