DNA damage

Mutationsin the narrow sense of the word refer to changes in the structure of the genetic material, i.e. in the DNA for most organisms, in which the sense of the genetic information is changed, without violating the syntactic rules of its writing.If the change violates these rules, for example, if depurination of certain nucleotides (or whole DNA sections) occurs or if a single-strand or double-strand break occurs, then this is termed DNA damage.The cell contains a number of enzyme systems capable of recognizing and repairing damaged sites.In some cases, the repair can be perfect and can renew the original information sense of the given DNA section.However, sometimes, repair is not possible and the cell can thus be permanently prevented from undergoing DNA replication and division.The repair very frequently renews the physical intactness of the DNA; however, it does not renew the original information content – mutations occur.Repair processes are apparently amongst the most important sources of mutations.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more