The role of unpaired sex chromosomes in spermatogenic failure*

In 1974 Miklos reviewed evidence suggesting an association between sex chromosome pairing failure and spermatogenic arrest. He proposed that distributed over all the chromosomes there are 'meiotic pairing sites' which must be 'saturated' by homologous pairing during pachytene. In unpaired regions these sites are 'activated', and set in motion a process which leads ultimately to the death of the cell. In the present 'extended abstract' we summarize studies we have carried out on XSxraO male mice, that substantiate the main tenets of Miklos' model. Miklos' model is then used as a basis for explaining data we have collected on a large series of XYY male mice.