On the origins of genetic variants

Two contrasting mechanisms responsible for the creation of genetic variants are described: one is the manifestation of the limited accuracy of the cellular machinery for DNA replication, the other results from the ability of cells to repair damaged DNA. Replication-dependent variants and those caused by episodical DNA damage enhance the probability that a small fraction of a cell population may survive a sudden (physical or biological) change of environmental conditions. Replication-independent variants arise during persistent but not immediately lethal stress (e.g. starvation) of a non-dividing population. The variants observed under these conditions are of selective advantage because they are able to cope with the particular stress situation. The molecular basis of their creation is a matter of intensive debate.