The presence of the tripartite ribbon within synapsed homologues has been reported for a large number of sexually reproducing organisms (over one hundred species, including fungi, plants, vertebrates and invertebrates). The absence of the ribbon in some species is associated with uncommon synaptic behaviour of meiotic prophase chromosomes (Drosophila melanogaster males, Drosophila melanogaster females homozygous for synapsis suppressing mutant C3G, and achiasmatic Dipteran species, reported by G. F. Meyer, 1964, Third European Regional Conference on Electron Microscopy). The tripartite ribbon, or synaptinemal complex, may therefore be assumed to be related to pairing of homologues at meiosis. The presence of the complexes and multi-complexes in non-meiotic cells such as insect obcyte nurse cells and spermatids suggests a somewhat broader function of the complexes. This is further supported by the occurrence of complexes in non-homologous paired chromosomes in the pollen mother cells of haploid tomato plants.
Proceedings of the European Regional Conference on Electron Microscopy, Delft 1960;1961