epigenetics ≠ Lamarckism An article at Heise online by challenging the titles "
rodents inheritance of acquired skills is on had lately in the media so popular" Lamarck was right! "train jumped.
It's in the article on current research in the neurobiology of mice. Briefly was a mouse line that due to a mutation has difficulty with memory, tested for memory performance. The researchers found that young mice of this line when they were brought up in an environment that calls for the brain - Toys, social interactions, movement - performed better in memory tests. So far, so well known. Surprisingly, it was now for the researchers found that the offspring had better memories of this special sponsored mice, even though they grew up not even in a stimulating environment.
The author of the Heise article sees the belated revenge by Lamarck to Darwin. Why this is false, and how the results should be interpreted more? Jean-Baptiste de Lamarck (1744 - 1829) was a French scientist with a very interesting life. Without a college degree, he wrote the then-standard work on the flora of France,
Flore Francoise , and was then a member of the Paris Academy of Sciences and employees of the Paris Botanical Garden. The site at the botanical garden was very poorly paid (depending on the source, even not at all), he had to otherwise provide an income: the publishing of other botanical books. This took place during the French Revolution, and while elsewhere were cut off heads in the city, received Lamarck a job and professor at the newly founded natural history museum - now responsible for insects and worms, but before you at this time to defend such a direction from above, a botanist would rather learn something new about animals.
Lamarck is known, however, until today for his theory of evolution developed in 1800. For while the idea of evolution, ie the formation of new species from older, for some time in early science haunted [1], still lacked a workable mechanism that would do this. Lamarck's view this was an inherent urge all organisms to evolve from a simple prototype to a better, more complex form out.
The most famous image, which describes the Lamarckian evolution takes, the giraffe, for example. Why do giraffes have such long necks? Because giraffes have their first or short necks elongated their lives over to the succulent leaves at the top to reach the trees, and inherited this so extended necks to their offspring. After several generations had then giraffes with long necks. The problem was to Lamarckism, 50 years later that Darwin had an idea for an evolutionary mechanism, and through natural selection could be not only loads data from fossils and extant species explain, but the long necks The giraffe: it had to do with the succulent leaves at the top in the trees, as Lamarck was still correct. In the population of giraffes, there were different neck lengths (variation), and if only the giraffes reached with the longest necks of the succulent leaves, then they also had more offspring inherited the long necks.
If in the media in recent months is about epigenetics, it is often evoked the Lamarckism. What is epigenetics? A precise definition of epigenetics is still, in general, one understands but heritable characteristics that are not encoded in the sequence of DNA (which would have to genetics). A epigenetic inheritance, it would, for example, if the level of expression of a gene is inherited (in the extremes, therefore, whether a gene is turned on or off). How could a piece of information to be passed if it is not inherited in the form of a DNA sequence? Of the various options shown so far I will briefly describe two here: a gene is not only the sequence that is later translated into a protein. Before this area is a section of DNA, which sets as a kind of (dimming) switch, the amount of protein produced by regulatory proteins bind to it - the promoter. By attaching methyl groups to cytosines (one of the four bases of DNA), promoters set aside be. This is not a change in DNA sequence, the cytosines are still sitting in place in the promoter. The methyl group is covalently bonded to the cytosine, ie is inherited in the usual way with the cytosine on to offspring. In the progeny of this gene will be shut down so well.
is the second epigenetic mechanism no change of bases necessary. In the nucleus, the DNA floating around not naked, but there are a number of structural proteins bound to them. Very important here are the histones, which are small spherical complexes (called nucleosomes) wrapped with DNA [2]. The winding of DNA is needed to several meters away irrepressible in a cell nucleus a few micrometres in diameter. There are various condensation stages, the strongest of which the known metaphase chromosomes. The expression of genes in such a condensed state, but no longer possible.
The regulation of these condensation via modification of histones, attaching methyl groups, for example, increasing the degree of condensation, while an attached acetyl group decreases it [3]. It is therefore possible for the cell to regulate the expression of genes in a relatively small region of a chromosome.
In recent years, is now much evidence for an epigenetic inheritance Properties found which an organism acquires during its life. The memory performance of mice in the above linked Heise article is an example, but also
increased recombination in Arabidopsis plants after UV-irradiation of their parents covered. Superficially one can understand why some people think of the inheritance of the acquired characteristics of Lamarck, or why the discussion of epigenetics in the media often Lamarckism is thrown. But there are several reasons why you can not equate those two concepts!
- While all current research described an external influence produced the inherited characteristics in organisms, Lamarck himself vehemently protested against such environmental influences on inheritance. In his view, finally lived each organism occupies a driving force that compelled him to evolve more complex. According to Lamarck
- such acquired characteristics accumulate in a population, because they can not be lost. Epigenetics is a very dynamic and unstable process effects such as the Heise article is lost after several generations.
- epigenetics still rests on a genetic basis. The epigenetic modifications are generated by proteins that are encoded in the genome very conventionally. Epigenetically inherited characteristics are also subject to evolutionary forces such as selection and genetic Drift. So WIN Darwin, Lamarck FAIL.
What I now do not quite understand: Why is Author Ben Swan's article so that the impression of the inexperienced reader, current research shows the problems with Darwin's evolution theory, which could be explained by the repressed idea of the underdog Lamarck? And why is the entire article, the term epigenetics not once, despite being in a
article of Technology Review sister product (of which the Heise article was written off) was discussed in detail? Since the text has come for Heise online relationships are relatively long, certainly not for lack of space.
Funnily point the way: In Technology Review also reported on a second, similar study in mice, in which poor mothers had offspring that were also bad parents. This remains the Heise article only option, "for example, that the impact of early child abuse can skip generations [...]."
Oh, and both thumbs up for the many commentators on the article, criticizing not only the quality of the article, but also the inevitable
creationists in their barriers have .
[1] For example, Darwin's grandfather Erasmus Darwin about
a beautiful poem written .
[2] Histone proteins are positively charged, DNA negative.
[3] quite so simple is not. The effect is affected by changes in the histone, the amino acid changes, and even the type of attached group. Based on the genetic code, this regulation as
histone code was called.
