The left panel corresponds to an artistic collage, showing Spo11-complexes (blue and yellow shapes) that cleave pieces out of chromosomes (shown in black). Red halos depict DNA-damage signalling. Liberated pieces carry a part of the Spo11-complex on each end. The right panel shows observed chromosomal break sites at a meiotic recombination hotspot. Each arc labels start and end of an isolated fragment coming from a different cell. Wild-type fragments are in red, fragments from a mutant that doesn’t degrade longer fragments, are in blue. (c) Franz Klein, Chromosomenbiologie, Universität Wien
Meiosis is a specialized cell division process required to generate gametes, the reproductive cells of an organism. During meiosis, paternal and maternal chromosomes duplicate, pair, and exchange parts of their DNA in a process called meiotic recombination. In order to mediate this exchange of genetic material, cells introduce double strand breaks (DSBs) into their chromosomal DNA. Scientists from the lab of Franz Klein from the Department of Chromosome Biology at the Max Perutz Labs, a joint venture of the University of Vienna and the Medical University of Vienna, have now discovered that cells sometimes liberate DNA fragments at sites of paired, or double, DSBs. Whilst this presents an obvious risk of germline mutations as a consequence of erroneous repair or of integration of fragments from elsewhere at break sites, it may also be a source of evolutionary diversity. The study is published as a research article in Nature.