After a DNA molecule breaks, the broken ends search for an intact DNA region with the same sequence in order to get repaired. The image shows an artist impression of the contact point between a RecA-protein DNA molecule (the "broken end"; horizontal) and a DNA molecule (vertical), where it is probed whether both molecules have the same sequence. If they do not, they will break the contact. If the same sequence is found however, the molecules stably bind and the repair process is initiated. The present study discovered the mechanism of the recognition process from dual molecule experiments where individual DNA molecules can be manipulated with beads.