Weismann barrier

The Weismann barrier is the hypothesis that the acquisition of information acquired characteristics (so-called modifications ) is impossible in the genetic material of germ cells and thus acquired characteristics are not inherited. It was formulated in 1883 by August Weismann. Evolutionary theorists before him (Jean -Baptiste de Lamarck, Charles Darwin) still went out of the possibility of inheritance of acquired characteristics.

Today's knowledge of geneticists about chromosomes and DNA was Weismann not yet available. He used the terms germplasm and body plasma. The germplasm was responsible for the transfer of genetic information, while the body plasma determine the expression of the organism. Information came from the germplasm in the body plasma and thus determined the expression of hereditary characteristics. Conversely, however, no information could get out of the body plasma in the germ plasm. External influences a change in the individual characteristics is possible, the germ plasm but would in no way be affected.

Weismann's ideas were supported by the findings of developmental biology and genetics. Developmental biologists in animals identified a cell line of the egg to the germ cells, the so called germline which remains disconnected from the development of the body's cells. In unicellular organisms, fungi and plants, there is no separate germline. However, Weismann's argument was not based on the existence of a physical barrier between the body and plasma germplasm, but the fact that there is no plausible mechanism that can be incorporated with the acquired properties in the structure of the germ cells. This was " as if a German telegram to China were up there the same in Chinese. "

During the 20th century, doubts about the Weismann barrier increasingly came on. The enzyme reverse transcriptase and other mechanisms allow for targeted changes to the genetic information. Some studies indicate that over the maternal ova, information can be passed to the next generation, which were not created in the genome, but were only acquired in the course of life. A Weismann student pointed out in 1923 that could be explained so that some human behaviors, and distanced himself early on by the neo -Darwinian orientation. Epigenetics provides numerous arguments that contradict the hypothesis of Weismann.