Meiotic centromere behaviors in budding yeast.

<p><b>A.</b> In meiosis of budding yeast, Zip1 (orange) mediates centromere coupling (green arrowheads) between non-homologous partner chromosomes (light blue and purple). As the cell proceeds through later stages of meiosis, homologs pair and the mature synaptonemal complex (SC) structure zips the chromosomes together. After pachytene, the SC disassembles, except at the centromeres (blue arrowhead). <b>B.</b> The Zip1 protein is predicted to have globular domains at its ends spanning a longer coiled-coil and forms parallel dimers with N-termini in the center of the SC (denoted by N) and the C-termini along the axial elements (denoted by C). <b>C</b>. We evaluated the same nine <i>ZIP1</i> deletion mutants previously described by Tung and colleagues (Tung & Roeder, 1998). The mutations are named for their relative position along the genetic sequence–N for N-terminus, M for middle region, and C for C-terminus. The approximate SC structure formed in each mutant as described by Tung and Roeder (1998) is shown. <b>D.</b> The areas shaded in blue correspond to deletions (above) that significantly disrupted centromere coupling. Those shaded in green correlate with deletions that significantly disrupted achiasmate segregation. Note that not all deletions were screened for achiasmate segregation defects because some caused a meiotic arrest.