Cancer cells often contain translocation mutations, in which parts of the genome are swapped between chromosomes. For the first time, scientists have been able to watch these accidents as they happen in living cells.

Researchers led by Tom Misteli at the National Cancer Institute in Bethesda, Maryland, coupled ultra-high-throughput techniques for time-lapse imaging with a system for 'snapping' DNA strands in chromosomes, and watched what happened to DNA fragments in cultured cells. On rare occasions, the breaks occurred in separate chromosomes and the broken ends attached to the wrong partners. These translocations formed within hours of a break and were guided by the cell's repair machinery. The work will allow further study of how and when chromosomal mix-ups occur.

Science 341, 660–664 (2013)