Résumé
In the yeast Saccharomyces cerevisiae, meiotic
recombination is initiated by transient DNA double-strand breaks (DSBs)
that are repaired by interaction of the broken chromosome with its
homologue. To identify a large number of DSB sites and gain insight
into the control of DSB formation at both the local and the whole
chromosomal levels, we have determined at high resolution the
distribution of meiotic DSBs along the 340 kb of chromosome III. We
have found 76 DSB regions, mostly located in intergenic
promoter-containing intervals. The frequency of DSBs varies at least
50-fold from one region to another. The global distribution of DSB
regions along chromosome III is nonrandom, defining large (39–105 kb)
chromosomal domains, both hot and cold. The distribution of these
localized DSBs indicates that they are likely to initiate most
crossovers along chromosome III, but some discrepancies remain to be
explained.