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The best of BlackBerry!
Evolution caught in the act
Jan 2, 2010
US-German team measures how quickly genomes change
Mutations are the raw material of evolution. Charles Darwin already recognized that evolution depends on heritable differences between individuals: those who are better adapted to the environment have better chances to pass on their genes to the next generation. A species can only evolve if the genome changes through new mutations, with the best new variants surviving the sieve of selection. Scientists at the Max Planck Institute for Developmental Biology in Tübingen, Germany, and Indiana University in Bloomington have now been able to measure for the first time directly the speed with which new mutations occur in plants. Their findings shed new light on a fundamental evolutionary process. They explain, for example, why resistance to herbicides can appear within just a few years. (Science, January 1, 2010)
Fig.: Different mutants of Arabidopsis thaliana.
Image: Detlef Weigel
“While the long term effects of genome mutations are quite well understood, we did not know how often new mutations arise in the first place,” said Detlef Weigel, director at the Max Planck Institute in Germany. It is routine today to compare the genomes of related animal or plant species. Such comparisons, however, ignore mutations that have been lost in the millions of years since two species separated. The teams of Weigel and his colleague Michael Lynch at Indiana University therefore wanted to scrutinize the signature of evolution before selection occurs. To this end, they followed all genetic changes in five lines of the mustard relative Arabidopsis thaliana that occurred during 30 generations. In the genome of the final generation they then searched for differences to the genome of the original ancestor.
The painstakingly detailed comparison of the entire genome revealed that in over the course of only a few years some 20 DNA building blocks, so called base pairs, had been mutated in each of the five lines. “The probability that any letter of the genome changes in a single generation is thus about one in 140 million,” explains Michael Lynch. To put it differently, each seedling has on average one new mutation in each of the two copies of its genome that it inherits from mum and dad. To find these tiny alterations in the 120 million base pair genome of Arabidopsis was akin to finding the proverbial needle in a haystack, says Weigel: “To ferret out where the genome had changed was only possibly because of new methods that allowed us to screen the entire genome with high precision and in very short time.” Still, the effort was daunting: To distinguish true new mutations from detection errors, each letter in each genome had to be checked 30 times.
The number of new mutations in each individual plant might appear very small. But if one starts to consider that they occur in the genomes of every member of a species, it becomes clear how fluid the genome is: In a collection of only 60 million Arabidopsis plants, each letter in the genome is changed, on average, once. For an organism that produces thousands of seeds in each generation, 60 million is not such a big number at all.
Apart from the speed of new mutations, the study revealed that not every part of the genome is equally affected. With four different DNA letters, there are six possible changes—but only one of these is responsible for half of all the mutations found. In addition, scientists can now calculate more precisely when species split up. Arabidopsis thaliana and its closest relative, Arabidopsis lyrata, differ in a large number of traits including size and smell of flowers or longevity: Arabidopsis lyrata plants often live for years, while Arabidopsis thaliana plants normally survive only for a few months. Colleagues had previously assumed that only five million years had passed by since the two species went their separate ways. The new data suggest instead that the split occurred already 20 million years ago. Similar arguments might affect estimates of when in prehistory animals and plants were first domesticated.
On a rather positive note, the results of the US-German team show that in sufficiently large populations, every possible mutation in the genome should be present. Thus, breeders should be able to find any simple mutation that has the potential to increase yield or make plants tolerate drought in a better manner. Finding these among all the unchanged siblings remains nevertheless a challenging task. On the other hand, the new findings easily explain why weeds become quickly resistant to herbicides. In a large weed population, a few individuals might have a mutation in just the right place in their genome to help them withstand the herbicide. “This is in particular a problem because herbicides often affect only the function of individual genes or gene products,” says Weigel. A solution would be provided by herbicides that simultaneously interfere with the activity of several genes.
Turning to the larger picture, Weigel suggests that changes in the human genome are at least as rapid as in Arabidopsis: “If you apply our findings to humans, then each of us will have on the order of 60 new mutations that were not present in our parents.” With more than six billion people on our planet, this implies that on average each letter of the human genome is altered in dozens of fellow citizens. “Everything that is genetically possible is being tested in a very short period,” adds Lynch, emphasizing a very different view than perhaps the one we are all most familiar with: that evolution reveals itself only after thousands, if not millions of years.
[SD]
Original work:
Stephan Ossowski, Korbinian Schneeberger, José Ingnacio Lucas-Lledó, Norman Warthmann, Richard M. Clark, Ruth G. Shaw, Detlef Weigel and Michael Lynch
The rate and molecular spectrum of spontaneous mutations in Arabidopsis thaliana.
Science, January 1, 2010
Researchers Use New Acoustic Tools to Study Marine Mammals and Fish
Jan 2, 2010
A "pop-up" listening device is deployed off the Massachusetts coast. The autonomous recording units listen for ocean noise from all sources 24/7. (Credit: Denise Risch, NEFSC/NOAA) )
Over the past decade, researchers have developed a variety of reliable real-time and archival instruments to study sounds made or heard by marine mammals and fish. These new sensors are now being used in research, management, and conservation projects around the world, with some very important practical results. Among them is improved monitoring of endangered North Atlantic right whales in an effort to reduce ship strikes, a leading cause of their deaths.
“The tools available to both acquire and analyze passive acoustic data have undergone a revolutionary change over the last ten years, and have substantially increased our ability to collect acoustic information and use it as a functional management tool,” said Sofie Van Parijs, lead author and a bioacoustician at NOAA’s Northeast Fisheries Science Center laboratory in Woods Hole, Mass. “These tools have significantly improved monitoring of North Atlantic right whales and enhanced the efficacy of managing ship traffic to reduce ship strikes of whales through much of the western North Atlantic off the U.S. East Coast.”
Van Parijs is one of many researcher whose work is decribed this month in the journal Marine Ecology Progress Series. Her paper is one of about a dozen in a special theme issue focused on acoustics in marine ecology. Van Parijs, who currently heads the NEFSC’s Protected Species Branch, is also a co-author of a related paper on acoustic interference or masking, in which marine animals alter their use of sound as a result of changing background noise.
Large commercial ships routinely pass through feeding grounds for endangered North Atlantic right whales and other marine mammals. (Credit: Stellwagen Bank National Marine Sanctuary, NOAA)
Van Parijs and her colleagues focus on two types of acoustic sensors, real-time and archival. Real-time sensors are mounted on surface buoys, usually anchored or cabled to the ocean bottom, or deployed as arrays towed from a surface vessel. Archival sensors are affixed on bottom-moored buoys equipped with hydrophones to continuously record ocean sounds for long periods of time, often up to three months, before the sensors are temporarily recovered and their batteries refreshed. Some archiving sensors can be mounted of individual animals.
“Marine animals live their lives and communicate acoustically across different time and space scales and use sound for different reasons,” said Van Parijs. “We need to use the right tool in the right place for the right need. There is no ‘one size fits all’ when it comes to using technology in the ocean.”
Large whales move and communicate over great distances, while smaller whales and dolphins tend to communicate over smaller areas. Pinnipeds, the group of marine mammals that includes seals, walrus and sea lions, can breed on land, on ice or in the water, and move and communicate from small to medium distances. Human-produced sounds complicate the sensing problem by adding sounds to what can be a very noisy environment.
The use of passive acoustic monitoring is increasing as improved reliability and lower hardware and software costs provide researchers with a set of tools that can answer a broad range of scientific questions. This information can, in turn, be used in conservation management and mitigation efforts. While most of the new technologies have been applied in studies of whales and dolphins, the researchers say the sensors can also be used in studying pinnipeds, sirenians (manatees and dugongs), and fish.
In addition to Van Parijs and colleagues at NOAA’s Northeast and Southwest Fisheries Science Centers, co-authors on the article include researchers from Cornell University’s Bioacoustics Research Program, Instituto Baleta Jubarta in Brazil, Pennsylvania State University, Integrated Statistics, and the Alfred Wegener Institute for Polar and Marine Research in Germany.
Jerry! Jerry! (Oldies Club, fostered Oxfordshire)
Jerry is a big strapping lad, but he's very nice natured and adores people. He loves company so would really like a home with someone who can be around a lot during the day. He gets on well with other laid-back dogs and would be happy sharing his new home with a canine housemate.
Affectionate Bobby (Oldies Club, fostered Leicester)
Bobby is a sweet and gentle boy with simple needs - food and fuss! He's a quiet soul who is nervous of sudden movements and would dearly love to find a new home with his best friend, Alfie.
Chatty Alfie (Oldies Club, fostered Leicester)
Alfie is a gentle lurcher who loves to play but also enjoys relaxing. Despite being a mischievous lad, he's quite a sensitive soul and would dearly love to find a new home with his best friend, Bobby.
Pippa (Animal Helpline, Peterborough)
Pippa is a perfect all round GSD girl who enjoys walks, sleeping, playing with toys and getting treats. She is a true daddy's girl who loves people and gets along well with other dogs, especially bigger ones like herself. She prefers the quiet life and would make a perfect companion to an older couple or person.
Tub-E bathtub adds automation and style to your bathing ritual
Jan 2, 2010
Does anyone still take baths these days? While the speed and efficiency of a quick shower is hard to beat, there is something to be said for a long soothing hot soak in the tub. I'm just not sure I'd want to do it in the Tub-E.
Looking like a triumph of form over function, the undeniably cool looking Tub-E includes several high tech functions to make your bath time a bit more luxurious. A thermostatically controlled heater under the seat keeps the water at a constant temperature, so you won't be adding hot water to reheat the water every few minutes. Add to that its auto fill, auto empty, and auto clean cycles, plus the ability to inject various bath oils during the fill process, and you certainly have a few improvements over the centuries old basic tub. My main issue is that it just looks incredibly uncomfortable.
The Tub-E is available from Wild Terrain Designs. No word on the price.
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