A class of small RNAs inherited from the mother determines offspring's fertility trait
Hereditary information flows from parents to offspring not just through DNA but also through the millions of proteins and other molecules that cling to it. These modifications of DNA, known as "epigenetic marks," act both as a switch and a dial - they can determine which genes should be turned on or off, and how much message an "on" gene should produce.
Science & Technology
Space shuttle Endeavour undocked from the International Space Station this morning, and the two spacecraft are now orbiting Earth in tandem. Endeavour is scheduled to land in Florida on Sunday, Nov. 30th.
Between now and then, many sky watchers (especially those in Europe) will be able to see the shuttle and the space station cutting across the night sky together--a rare and beautiful "double flyby."
Between now and then, many sky watchers (especially those in Europe) will be able to see the shuttle and the space station cutting across the night sky together--a rare and beautiful "double flyby."
It seems we got off lightly in the cosmic lottery. Deadly comet impacts may be much rarer in our solar system than in others nearby.
We can't directly measure the rate of comet collisions in other solar systems but we can detect signs of the dust that such smashes kick up because the dust gets warmed by the star and so gives off infrared radiation. That radiation shows up as extra infrared in the spectrum of light coming from the star. Because such dust should dissipate quickly, it is thought to provide a good snapshot of the recent collision rate.
Jane Greaves of the University of St Andrews, UK, analysed observations by the Spitzer Space Telescope and found that the vast majority of sun-like stars near us have more dust than our solar system does and therefore have had more collisions in their vicinity. Our solar system may be one of the few that have been safe for life. Greaves presented her results at the Cosmic Cataclysms and Life symposium in Frascati, Italy, this month.
We can't directly measure the rate of comet collisions in other solar systems but we can detect signs of the dust that such smashes kick up because the dust gets warmed by the star and so gives off infrared radiation. That radiation shows up as extra infrared in the spectrum of light coming from the star. Because such dust should dissipate quickly, it is thought to provide a good snapshot of the recent collision rate.
Jane Greaves of the University of St Andrews, UK, analysed observations by the Spitzer Space Telescope and found that the vast majority of sun-like stars near us have more dust than our solar system does and therefore have had more collisions in their vicinity. Our solar system may be one of the few that have been safe for life. Greaves presented her results at the Cosmic Cataclysms and Life symposium in Frascati, Italy, this month.
© C GSF/Caltech/JPL/NASA
This artist's concept illustrates a comet being torn to shreds around a dead star, or white dwarf, called G29-38.
This artist's concept illustrates a comet being torn to shreds around a dead star, or white dwarf, called G29-38.
Researchers say they have located the world's oldest stash of marijuana, in a tomb in a remote part of China.
The cache of cannabis is about 2,700 years old and was clearly "cultivated for psychoactive purposes," rather than as fibre for clothing or as food, says a research paper in the Journal of Experimental Botany.
The cache of cannabis is about 2,700 years old and was clearly "cultivated for psychoactive purposes," rather than as fibre for clothing or as food, says a research paper in the Journal of Experimental Botany.
Is this the dark side speaking?
A concatenation of puzzling results from an alphabet soup of satellites and experiments has led a growing number of astronomers and physicists to suspect that they are getting signals from a shadow universe of dark matter that makes up a quarter of creation but has eluded direct detection until now.
Maybe.
"Nobody really knows what's going on," said Gordon Kane, a theorist at the University of Michigan. Physicists caution that there could still be a relatively simple astronomical explanation for the recent observations.
A concatenation of puzzling results from an alphabet soup of satellites and experiments has led a growing number of astronomers and physicists to suspect that they are getting signals from a shadow universe of dark matter that makes up a quarter of creation but has eluded direct detection until now.
Maybe.
"Nobody really knows what's going on," said Gordon Kane, a theorist at the University of Michigan. Physicists caution that there could still be a relatively simple astronomical explanation for the recent observations.
© Karl Grossschmidt
A referee looks on as two distinct types of gladiators battle to the death on this relief found in the gladiator graveyard at Ephesus. The man in the middle--a lumbering secutor--has lost his shield, leaving him vulnerable to the lightly armored retiarus at right
A referee looks on as two distinct types of gladiators battle to the death on this relief found in the gladiator graveyard at Ephesus. The man in the middle--a lumbering secutor--has lost his shield, leaving him vulnerable to the lightly armored retiarus at right
Jupiter has a rocky core that is more than twice as large as previously thought, according to computer calculations by a University of California, Berkeley, geophysicist who simulated conditions inside the planet on the scale of individual hydrogen and helium atoms. The results were published in Astrophysical Journal Letters.
© Space Daily
The simulation suggests that the core is made of layers of metals, rocks and ices of methane, ammonia and water, while above it is an atmosphere of mostly hydrogen and helium. At the center of the rocky core is probably a metallic ball of iron and nickel, just like Earth's core.
The simulation suggests that the core is made of layers of metals, rocks and ices of methane, ammonia and water, while above it is an atmosphere of mostly hydrogen and helium. At the center of the rocky core is probably a metallic ball of iron and nickel, just like Earth's core.
Legend says the afterlife for ancient Mayas was a terrifying obstacle course in which the dead had to traverse rivers of blood, and chambers full of sharp knives, bats and jaguars.
Now a Mexican archaeologist using long-forgotten testimony from the Spanish Inquisition says a series of caves he has explored may be the place where the Maya actually tried to depict this highway through hell.
The network of underground chambers, roads and temples beneath farmland and jungle on the Yucatan peninsula suggests the Maya fashioned them to mimic the journey to the underworld, or Xibalba, described in ancient mythological texts such as the Popol Vuh.
Now a Mexican archaeologist using long-forgotten testimony from the Spanish Inquisition says a series of caves he has explored may be the place where the Maya actually tried to depict this highway through hell.
The network of underground chambers, roads and temples beneath farmland and jungle on the Yucatan peninsula suggests the Maya fashioned them to mimic the journey to the underworld, or Xibalba, described in ancient mythological texts such as the Popol Vuh.
© JPL/NASA
Scientists first saw a plume of water vapor and dust shooting from the moon's south pole in 2005.
Research later determined that the water geysers are gushing out at about 1,000 miles (1,609 kilometers) an hour from a series of 100-mile-long (161-kilometer-long) fissures dubbed tiger stripes.
© iStockphoto/Monique Rodriguez
Aging dog. Researchers have uncovered what may be a universal cause of aging, one that applies to both single cell organisms such as yeast and multicellular organisms, including mammals.
Aging dog. Researchers have uncovered what may be a universal cause of aging, one that applies to both single cell organisms such as yeast and multicellular organisms, including mammals.
The mechanism probably dates back more than one billion years. The study shows how DNA damage eventually leads to a breakdown in the cell's ability to properly regulate which genes are switched on and off in particular settings.
Like our current financial crisis, the aging process might also be a product excessive deregulation.
Researchers have discovered that DNA damage decreases a cell's ability to regulate which genes are turned on and off in particular settings. This mechanism, which applies both to fungus and to us, might represent a universal culprit for aging.
Comment: While comet impacts may be "much rarer" in our solar system than others, it certainly does not mean they do not strike ours. For a more enlightening and detailed study, read Forget about Global Warming, We are One Step From Extinction!