Posted on 01/02/2010 10:57:44 AM PST by Restore
Mutations are the raw material of evolution. Scientists at the Max Planck Institute for Developmental Biology in Tubingen, 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.
"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.
Er...no, Al's warming didn't happen.
“Er...no, Al's warming didn't happen.”Wha?
Strictly speaking, in terms of scientific philosophy, there is no "factual proof" of any theory. Technically, there are only hypotheses which have not yet been disproved.
I mention this in answer to those who claim "Evolutionism" is just another "religion." It's not. It's a theory with lots of factual data to support it, and hypotheses which have never been disproved.
The data comes from virtually every scientific field -- biology, geology, chemistry, paleontology, genetics, physics, astronomy, etc., etc.
Now the idea of "random mutations" is itself evolving from hypothesis to theory, to scientific data -- as demonstrated by this particular article.
When "random mutations" can be measured, quantified, analyzed and tracked, then the idea is no longer a hypothesis or even a theory, but simply confirmed scientific data.
btw, great work freedumb2003. Much enjoy and appreciate what you do. :-)
the whole carbon data thing has been disproved and their are still people using that as factual data.
Sorry pal, but I don't remember reading about a theory of "the whole carbon data thing." Is that somewhere on Wikipedia? ;-)
But perhaps you can cite for us all the peer reviewed scientific article in which "the whole carbon data thing" was conclusively disproved?
Very simply put, too many things are unknown to allow the carbon dating process to be as accurate as many proclaim it to be. Factors as diverse as changes in the earth’s magnetic field and changes in the amount of carbon available to organisms in times past could translate into perceivable differences in the carbon ratios in artifacts and remains from ancient times. Even changes in the atmosphere itself could impact this carbon ratio. We know that changes such as these have occurred over time. They are still occurring today in fact.
http://www.angelfire.com/mi/dinosaurs/carbondating.html
that should do it if u need more let me know
Oh, I get it. "carbon data" = "carbon dating" = "radiocarbon dating".
"Radiocarbon dating, or carbon dating, is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 58,000 to 62,000 years."The technique of radiocarbon dating was developed by Willard Libby and his colleagues at the University of Chicago in 1949... He first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge for which the age was known from historical documents."
Carbon dating is only one of many methods, radiometric and others, used to estimate ages of ancient materials, including:
And these are far from the only methods of establishing ancient time lines. But, performed properly, they can be amongst the most consistent and reliable:
"Finally, correlation between different isotopic dating methods may be required to confirm the age of a sample. For example, a study of the Amitsoq gneisses from western Greenland used five different radiometric dating methods to examine twelve samples and achieved agreement to within 30 Ma on an age of 3,640 Ma."
Obviously, any of these tests might be performed incorrectly, contaminants introduced, external factors improperly accounted for, etc. But there is no scientific proof, none, which tells us these test are necessarily largely inaccurate, even if done correctly.
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