A mutation in Caenorhabditis elegans that increases recombination frequency more than threefold.

In higher organisms the rate of recombination between genetic loci is presumably responsive to selective pressure. Recently, selective pressures and mutational events that influence recombination have been reviewed. Mutational sites and chromosomal rearrangements that enhance or suppress recombination frequency in specific regions are known, but general mechanisms that enhance recombination have not yet been discovered. We describe here the isolation and characterisation of a strain of the hermaphroditic nematode, Caenorhabditis elegans, that has a recombination frequency at least threefold higher than that found in the wild type. In this strain, rec-1, the number of reciprocal recombination events between linked loci is increased. This is true for all pairs of linked loci studies so far. The high recombination strain behaves as if it carries a classical recessive mutation, although a second mutation exists which can alter the recessive behaviour of rec-1.