Germ line therapy

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Germ line therapy is a method (not yet realized in humans) to cure inherited diseases that are based on a genetic defect in the offspring of a carrier of a defective gene or to prevent the inheritance of this genetic defect. The idea of ​​germline therapy is that a genetically "repaired" chromosome becomes part of the zygote during fertilization and, through the subsequent mitotic cell division, becomes part of all body cells in the course of embryonic development , so that the hereditary disease present in the parent generation no longer occurs in the offspring , can no longer be inherited, and that the donor gene should perform normal functions in the offspring's body.

To do this, in the nucleus of a living egg cell or sperm cell (or on cells of the tissue from which these germ cells originate) on the chromosome that contains the genetic defect, the relevant DNA section must be genetically removed (with restriction enzymes ) and a healthy one at precisely this point Donor gene can be used without affecting the life functions. Furthermore, it would have to be possible to manage this gene manipulation on the DNA in such a way that no other genome sections also incorporate the donor gene in an inappropriate place.

Such interventions are sometimes already successful in lower organisms. Experiments on plants and animals are carried out in genetic engineering laboratories ( animal experiments ). However, these always result in high failure rates, i.e. H. The result is a high percentage of embryos which, due to unintentional changes in previously healthy parts of their genome, have newly emerging malformations, from which they often die. In the case of the survivors, the unintentionally occurring changes are also part of their genetic makeup, so that they pass these on to their offspring via the germ line .

Germ line therapy is banned in Germany according to Section 5 of the Embryo Protection Act of 1990, as it involves an artificial change in the genetic information of human germ line cells . Only somatic gene therapy is permitted , since the donor genes , which are only introduced into certain tissues of the body , do not reach the germ line and therefore no changes in the genetic material are to be expected.

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