Category C - full version without watermark 720x576 (check terms and conditions at www.teledesign.de) The version with watermark is for free to embed - Description: As a rule incorrectly paired nucleotides are detected after the replication process by special enzymes, they are excised and replaced by the correct base. This is a very efficient repairing system as it reduces mutation rate to one in a billion. Whereas the pairs are well conserved within the double helix, within the single strands another source of errors may arise: If there are frequent series of G C these can complementarily bind on the single strand and form loops that cannot be read during replication. There is another repairing system looking to this kind of errors -- which may however insert too many G C pairs. The DNA length may be minimally changed by these processes. The corrections are done within a time frame of several minutes.