Spontaneous mitotic recombination in Schizosaccharomyces pombe: origin of the increased recombination rates in a UV-sensitive mutant

The UV sensitive mutant rad2-44 of Schizosaccharomyces pombe increases mitotic gene conversion and crossover rates about 10-fold but has little or no effect on meiotic recombination. As in rad2 super(+) )recombination events on different chromosomes are coincidental in rad2-44, indicating that mitotic recombination takes place in a subpopulation of competent cells. However, the coefficient of coincidence is smaller in the mutant, whereas recombination rates among the competent cells are the same as in rad2 super(+). This suggests that rad2-44 increases mitotic recombination by enhancing the fraction of competent cells.