The return of copy-choice in DNA recombination.

In a recent publication, d'Alençon et al.(1) presented evidence that a form of non-homologous DNA recombination involving direct repeats is dependent upon the replication of the DNA. In addition, density-labeling experiments showed that after recombination was stimulated, progenies were present only in molecules that had undergone complete replication. These observations are consistent with a replicative and not a breakage-and-rejoining model for the DNA recombination events. These two models had of course been contrasted many years ago in mechanistic studies of homologous DNA recombination. It is therefore interesting to place the latest findings of d'Alençon et al. in this historical context.