On Spo16 and the Coefficient of Coincidence

spo16 mutants in yeast were reported to have reduced map lengths, a high frequency Of non-disjunction in the first. meiotic division, and essentially unchanged coefficients of coincidence. Were all crossing over in yeast subject to interference, such data would suggest that the designation of recombination events to become crossovers is separable from the implementation of that crossing over. In the presence of coexisting interference and noninterference phases of crossing over, however, lack of change in the coefficient of coincidence may show only that spo16 reduces crossing over in the two phases by a similar factor.