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first_imgThis story is not about Enron and Exxon, but about introns and exons.  The proportions of the scandals they are causing in evolutionary theory, however, may be comparable.    Introns are spacers between genes.  For several decades now, it has been a puzzle why they are there, and why a complex machine called a spliceosome takes them out and joins the active genetic parts – the exons – together. Only eukaryotes have spliceosomes, though; mitochondria have “group II introns” and some mRNAs may have them.  Their presence and numbers in various groups presents a bewildering array of combinations.  Figuring out a phylogenetic tree for introns has eluded evolutionary geneticists, as has understanding their origin and functions (02/18/2005).  Why do genes come in pieces that have to be reassembled?     William Martin and Eugene Koonin said in Nature1 that “The discovery of introns had a broad effect on thoughts about early evolution.”  Some theories have been falsified, and others remain in the running.  Consider the scope of the problems:A current consensus on introns would be that prokaryotes do indeed have group II introns but that they never had spliceosomes; hence, streamlining in the original sense (that is, loss of spliceosomal introns) never occurred in prokaryotes, although it did occur in some eukaryotes such as yeast or microsporidia.  An expansion of that consensus would be that spliceosomes and spliceosomal introns are universal among eukaryotes, that group II introns originating from the mitochondrion are indeed the most likely precursors of eukaryotic mRNA introns and spliceosomal snRNAs, and that many—conceivably most—eukaryotic introns are as old as eukaryotes themselves.  More recent are the insights that there is virtually no evolutionary grade detectable in the origin of the spliceosome, which apparently was present in its (almost) fully fledged state in the common ancestor of eukaryotic lineages studied so far, and that the suspected source of introns—mitochondria, including their anaerobic forms, hydrogenosomes and mitosomes—was also present in the common ancestor of contemporary eukaryotes (the only ones whose origin or attributes require explanation).    This suggests that intron origin and spread occurred within a narrow window of evolutionary time: subsequent to the origin of the mitochondrion, but before the diversification of the major eukaryotic lineages.  This, in turn, indicates the existence of a turbulent phase of genome evolution in the wake of mitochondrial origin, during which group II introns invaded the host’s chromosomes, spread as transposable elements into hundreds—perhaps thousands—of positions that have been conserved to the present, and fragmented into both mRNA introns and snRNA constituents of the spliceosome.This means that a complex molecular machine, the spliceosome (09/17/2004, 09/12/2002), appeared fully formed almost abruptly, and that the intron invasion took place over a short time and has not changed for hundreds of millions of years.  They submitted a new hypothesis:Here we revisit the possible evolutionary significance of introns in light of mitochondrial ubiquity.  We propose that the spread of group II introns and their mutational decay into spliceosomal introns created a strong selective pressure to exclude ribosomes from the vicinity of the chromosomes—thus breaking the prokaryotic paradigm of co-transcriptional translation and forcing nucleus-cytosol compartmentalization, which allowed translation to occur on properly matured mRNAs only.   (Emphasis added in all quotes.)But this means that the nucleus, nucleolus and other complex structures also had to appear in a very brief period of time.  It means that the engulfed organism that somehow became mitochondria had to transfer its introns rapidly into a genome lacking a nucleus.  It means the nucleus had to evolve quickly to segregate the new mitochondrial genes from the nuclear genes.  A lot had to happen quickly.  “This bipartite cell would not be an immediate success story: it would have nothing but problems instead,” they admitted, but they believed that natural selection would favor the few that worked out a symbiotic relationship with their new invaders.    This is not the end of the problems.  The group II introns would have had to embed themselves with reverse transcriptase and maturase without activating the host’s defenses, then evolve into spliceosome-dependent introns and remain unchanged forever after.  Then those embedded group II introns would undergo mutational decay, interfering with gene expression.  Will this work without some miracles?A problem of a much more severe nature arises, however, with the mutational decay of group II introns, resulting in inactivation of the maturase and/or RNA structural elements in at least some of the disseminated copies.  Modern examples from prokaryotes and organelles suggest that splicing with the help of maturase and RNA structural elements provided by intact group II introns in trans could have initially rescued gene expression at such loci, although maturase action in trans is much less effective than in cis.  Thus, the decay of the maturase gene in disseminated introns poses a requirement for invention of a new splicing machinery.  However, as discussed below, the transition to spliceosome-dependent splicing will also impose an unforgiving demand for inventions in addition to the spliceosome.A spliceosome is not an easy thing to invent; it has five snRNAs and over 200 proteins, making it one of the most complex molecular machines in the cell.  Not only that, they appeared in primitive eukaryotes and have been largely conserved since.  Perhaps the miracles can be made more believable by dividing them into smaller steps:It seems that the protospliceosome recruited the Sm-domain, possibly to replace the maturase, while retaining group II RNA domains (snRNAs) ancestrally germane to the splicing mechanism.  While the later evolution of the spliceosome entailed diversification with the recruitment of additional proteins—leading to greater efficiency—the simpler, ancestral protospliceosome could, in principle, rescue expression of genes containing degenerate group II introns in a maturase-independent manner, but at the dear cost of speed.Will a lateral pass from maturase to incipient spliceosome during a long field run lead to a touchdown?  If a stumbling protospliceosome could survive, in spite of vastly decreased translation rate, it might have been able to run the distance with natural selection’s encouragement, they think.  Players would be falling left and right in this “extremely unhealthy situation,” they say, and “the prospects of any descendants emerging from this situation are bleak.”  How could the game go on, then?  “The only recognizable mechanism operating in favour of this clumsy chimaera is weakened purifying selection operating on its exceptionally small initial population.”  Purifying selection means weeding out losers, not adding new champions.  “Finding a solution to the new problem of slow spliceosomes in the presence of fast and abundant ribosomes required an evolutionary novelty.”    They winnow down the possibilities.  Getting instant spliceosomes smacks too much of an improbable feat.  Getting rid of spliceosomal introns from DNA apparently did not occur.  Their solution?  The invention of the nucleus, where slow spliceosomes could operate without competition from fast ribosomes.    This adds new miracles, however.  The nucleus has highly complex pores that permit only authenticated molecules into the inner sanctum.  They think, however, that it must have happened, somehow: “Progeny that failed to physically separate mRNA processing from translation would not survive, nor would those that failed to invent pore complexes to allow chromosome-cytosol interaction.”  So pick your miracles: since necessity is the mother of invention, “The invention of the nucleus was mandatory to allow the expression of intron-containing genes in a cell whose ribosomes were faster than its spliceosomes.”    The near-miraculous arrival of the nucleus is underscored by other feats it performs: “In addition to splicing, eukaryotes possess elaborate mRNA surveillance mechanisms, in particular nonsense-mediated decay (NMD), to assure that only correctly processed mature mRNAs are translated, while aberrant mRNAs and those with premature termination codons are degraded.”  How could this originate?  Again, necessity must have driven the invention: “The initial intron invasion would have precipitated a requirement for mechanisms to identify exon junctions and to discriminate exons (with frame) from introns (without frame), as well as properly from improperly spliced transcripts.  Thus, NMD might be a direct evolutionary consequence of newly arisen genes-in-pieces.”  But then, if it is verified that some translation occurs in the nucleus, that would be “difficult to reconcile with our proposal.”    They ended with comparing their hypothesis with others.  “Our suggestion for the origin of the nucleus differs from previous views on the topic,” they boasted, “which either posit that the nuclear membrane was beneficial to (not mandatory for) its inventor by protecting chromosomes from shearing at division, or offer no plausible selective mechanism at all.”  At least theirs is simpler and includes some requirements to select for the cells with the best inventors – or the ones with the luckiest miracles.1Martin and Koonin, “Hypothesis: Introns and the origin of nucleus-cytosol compartmentalization,” Nature 440, 41-45 (2 March 2006) | doi:10.1038/nature04531.Was any of this storytelling useful?  The shenanigans they pulled, couched in biochemical jargon, can be summarized by two principles in their own imaginations: (1) since the cell needed these superbly-crafted machines, it had to invent them somehow, and (2) since evolution is a fact, it had to happen somehow.  Do you catch any hint of a mechanism for actually inventing a 200-protein supermachine that would actually work?  Did you find any hint that any cell any time had a “protospliceosome” that only worked half-way?  All this was pure fiction built on childlike faith in evolution.    Presenting a hypothesis in science is fine, but how would they ever test something like this?  They offered a few tests that could discriminate between their just-so story and other just-so stories, but nothing that could explain how a spliceosome, or a nuclear membrane with its elaborate pore complexes, or nonsense-mediated decay could have been invented from scratch just because a cell needed these things.    Would that evolutionists would get off this storytelling kick and do something useful with their lives.  Let’s find a cure for cancer.  Let’s find better sources of energy, and think of ways to reduce risks of disease and terrorism, and use science to improve our lives and our world.  Stringing together uncooperative data into a fictional account of prehistory will accomplish nothing and is wasting time and money in a world desperately in need of the productive possibilities of true science.(Visited 10 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img read more

first_img24 July 2007South African petrochemical company Sasol has become the first in the world to register a project that uses a secondary catalyst to convert the greenhouse gas nitrous oxide into harmless nitrogen and oxygen, which could earn the company significant income through the sale of carbon credits.Sasol said in a statement on Monday that a share of the revenue derived from the carbon credit sales would be invested in local community-based sustainable development projects.A carbon credit – one credit is equivalent to a ton of carbon dioxide reduced – is a tradable permit scheme used as an incentive for countries and businesses to reduce their greenhouse gas emissions.Countries that have signed the Kyoto Protocol have fixed quotas for greenhouse emissions. The protocol’s clean development mechanism allows businesses to generate carbon credits, which can then be sold or exchanged with businesses that have exceeded their quota limits.Sasol Nitro, which commissioned its nitrous oxide emission abatement technology during the first quarter of 2007, expects to reduce greenhouse gas emissions by the equivalent of about a million tons of carbon dioxide a year.According to the company, one ton of nitrous oxide has the greenhouse impact equivalent to 310 tons of carbon dioxide.The technology will be used to reduce emissions at two nitric acid plants in Sasolburg in the Free State province and Secunda in Mpumalanga province.“This is the first time that a project using a secondary catalyst has been registered as a clean development mechanism project in terms of the Kyoto Protocol,” said Sasol Chemical Businesses’ group general manager Reiner Groh.The project offered “significant environmental benefits for Sasol, our local communities and South Africa,” Groh added.Sasol said it had developed the project with assistance from MGM International, a specialist in the development of greenhouse gas emission reduction projects worldwide, and Heraues, a provider of catalyst technology for nitric acid production facilities.SouthAfrica.info reporter Want to use this article in your publication or on your website?See: Using SAinfo materiallast_img read more

first_imgShare Facebook Twitter Google + LinkedIn Pinterest A mix of clouds and sun expected over the Ohio today as warm air continues to push into the region. We expect more clouds in the north, but better sunshine potential in the central and southern parts of the state. Southwest flow will continue through the day. A minor disturbance lingers over MI and southern Ontario this morning, and clouds from that will be drifting across Lake Erie and into northern Ohio.  We see chances of a few scattered to isolated showers in those areas, down to around US 20. WE do not expect anything of consequence through the day farther south.  However, clouds will be increasing as we move through the afternoon and evening.Rain and thunderstorms arrive tomorrow. However, we likely will not see much of that truly get here until mid to late afternoon and the moisture ramps up overnight tomorrow night through Thursday. That means tomorrow morning and afternoon we continue to see clouds build, but will see some sunshine too. The more sun we see, the bigger the concern will be for thunderstorms in the afternoon and at night, as we charge up the atmosphere with extra energy. The rains from tomorrow late afternoon through Friday will be from .5″-1.5″ with coverage near 100% .Then we see lingering rain through Saturday bringing up to another half inch of rain over 70% of Ohio. Clouds finally give way to better sun on Sunday, but perhaps not until the afternoon. The map at right shows system total rain potential through Sunday morning.Next week starts damp. Scattered showers return for Monday with 75% of Ohio seeing up to half an inch of rain. Tuesday scattered showers bring 40% coverage to the entire state with rain totals up to .25”. Then Wednesday afternoon we see the largest slug of moisture arrive with a frontal boundary. . Rain and thunderstorms Wednesday late afternoon through Thursday trigger totals of .25”-1” with 90% coverage.Partly to mostly sunny skies finally muscle back in for Friday. As we transition into the extended period, we keep dry weather in over most of the state for Saturday the 27th but have to look for showers from US 50 south. Partly sunny skies are expected for Sunday the 28th. If this pattern is realized, that will be a significant dry window for at least half of the state…but it comes after some pretty significant moisture to start next week.As we finish April and move into May, we have rain returning Monday evening, the 29th, and continuing through midday Tuesday, the 30th. This brings .25”-.75” with 80% coverage. It will be followed up with scattered showers for Wednesday, May first, with .2” or less expected. A dry finish to the 16 day period is anticipated at this time for the 2nd.last_img read more

first_imgThe birthplace of the American Industrial Revolution aims to become one of the greenest towns in MassachusettsThere is no firm schedule worked out quite yet, but over the next five to ten years Worcester, Massachusetts, will evaluate, strategize, build, and retrofit its way to a greener existence.The motivation for this transformation is rooted in a combination of ecological and economic ambitions, and it is building momentum. As a recent story published by the Worcester Telegram & Gazette pointed out, environmental concerns prompted the city, in 2006, to join the Local Governments for Sustainability, an international association of more than 1,000 local governments from 67 countries that is committed to sustainable development.Concerns about shrinking the town’s carbon footprint prompted the emergence of the Energy Task Force, originally an academic alliance that two years ago developed the town’s Climate Action Plan, which identifies strategies for reducing energy use and the emission of greenhouse gases.The Energy Task Force has since become the town’s official engine of green transformation. Using a share of the $482 million in federal stimulus funds allocated to Massachusetts over the next two years, the city aims to develop its long-range energy plan on the greenest terms possible, create jobs in green industries, and develop a science plan that keeps Worcester-based researchers ahead of the curve of newfangled green technology. (The town is home to Worcester Polytechnic Institute and Clark University.)Targeting residential retrofitsOne of the most effective ways to get Worcester’s green going is to improve energy efficiency in its existing buildings, and make the most it can of the $122 million in stimulus money the state has received for weatherization, David Angel, a Clark professor and member of the task force, told the Telegram & Gazette.“How do you improve energy efficiency in a place that is already built up?” he asked rhetorically. “Retrofitting residential space rather than focusing on new construction.”Energy efficiency retrofits could come into play in a major way in some of Worcester’s older homes. One such property, a four-bedroom, two-bath 1910 Victorian, whose listing at $339,900 is currently being promoted through a private-public program called Buy Worcester Now, has attracted a fair number of prospective buyers, but no offers as of yet.The listing broker, Jason Piedrasanta, points out that people who have toured the home like its leather wainscoting, wood floors, tiled fireplaces, formal layout, and approximately 2,480 sq. ft. of living space. But many are concerned about the cost of heating and cooling the building, whose aged windows leak air liberally.Piedrasanta points that out the house is prime candidate for the kind of green upgrade that is being touted by the city’s Energy Task Force. Although the Victorian’s double walls still insulate quite well, he says, window replacement would be among the most cost-effective single measures one could take to improve the home’s energy efficiency.last_img read more