Weismann barrier
The Weismann-Barrier is the hypothesis that the transfer of information of acquired properties (so-called modifications ) into the genetic information of germ cells is impossible and thus acquired properties cannot be inherited. It was formulated in 1883 by August Weismann and published in 1892 in his work Das Keimplasma: a theory of inheritance . Evolution theorists before him ( Jean-Baptiste de Lamarck , Charles Darwin ) assumed the possibility of inheritance of acquired properties.
theory
The current knowledge of geneticists about chromosomes and DNA was not yet available to Weismann. He used the terms germplasm and body plasma. The germ plasma is responsible for passing on the genetic information, while the body plasma determines the expression of the organism. Information got from the germ plasma into the body plasma and thus determined the expression of hereditary characteristics. Conversely, however, no information from the body plasma could get into the germ plasma. A change in the individual properties is possible through external influences, but the germplasm remains unaffected.
Weismann's ideas were supported by the findings of developmental biology and genetics. Developmental biologists identified a cell line in animals from the egg cell to the germ cells, the so-called germ line , which remains separate from the development of the body cells. There is no separate germ line in unicellular organisms, fungi and plants. However, Weismann's argumentation was not based on the existence of a physical barrier between body plasma and germplasm, but on the fact that there was no plausible mechanism with which acquired properties can be introduced into the structure of the germ cells. This is "like if a German telegram to China arrived there in Chinese."
In the course of the 20th century, doubts about the Weismann barrier arose. The enzyme reverse transcriptase and other mechanisms enable targeted changes in genetic information. Some studies indicate that the maternal egg cells can also be used to pass on information to the next generation that was not inherited in the genome but was acquired in the course of life. As early as 1923, Weismann's student Mathilde von Kemnitz pointed out that this could also explain some human behavior, and early on she distinguished herself from the neo-Darwinian orientation.
Works (selection)
- 1892: The germ plasm: a theory of heredity . Jena: Fischer.
literature
- Thomas Junker, Uwe Hoßfeld (2001): The discovery of evolution.- A revolutionary theory and its history. ISBN 3-534-14208-X
- Ernst Mayr (1994): ... and Darwin is right. - Charles Darwin, his teaching and the modern theory of evolution. ISBN 3-492-11959-X