DOUBLE MEIOTIC MUTANTS OF MAIZE - IMPLICATIONS FOR THE GENETIC-REGULATION OF MEIOSIS

To determine whether genes involved in various components of meiosis initiate and proceed independently of each other, a set of 14 meiotic mutants of maize (Zea mays L.), encompassing the functional limits of meiosis, was intercrossed pairwise and then selfed. Cosegregating F2 families were identified by meiotic examination and, among these, single plants expressing both mutations (double mutants) were cytologically analyzed. Expression of both mutant phenotypes within one plant indicated the two corresponding genes were independently expressed; the wild-type activity of one gene was not required for initiation or activity of the other. Observations from 12 double mutants indicate that an all-encompassing regulatory cascade at the level of the gene does not exist in meiosis. Instead, results suggest the independent control of genes involved in pairing, spindle formation, cytokinesis, and other meiotic events. Events that occur at the conclusion of meiosis were not found to depend on successful execution of events earlier in the cycle. Reduction division appears to be a merging of individual independent activities.