The onion species AUium amplectans includes both a triploid and a tetraploid variety. By light microscopy both varieties appear to have normal synapsis during pachytene of meiosis. However, the triploid does not form chiasmata and exhibits almost total asynapsis following pachytene. The tetraploid forms at least one chiasma per homologue and retains pairing through metaphase I. Electron-microsc...

A series of Tn5 transposases (Tnp's) with mutations at the conserved amino acid position W450, which was structurally predicted to be important for synapsis, have been generated and characterized. This study demonstrates that W450 is involved in hydrophobic (and possibly aromatic) contacts within the Tnp monomer that negatively regulate synaptic complex formation.

Meiotic pairing in the nematode Caenorhabditis elegans is facilitated by chromosomal sites known as pairing centers that are tethered to the nuclear envelope. Sato et al. (2009) and Penkner et al. (2009) provide insight into how proteins linking pairing centers and the microtubule cytoskeleton mediate homolog pairing and restrict synapsis to homologous pairs of chromosomes.