The number of late nodules is approximately the same as the number of genetic cross-over events . The width of the SC is increased by engineering the ZIP1 gene to produce a larger protein. Other Pages Interpretations Contrary to intuition, SC formation is not necessary for strand exchange between DNA duplexes. SC formation is necessary for cross over interference . The ZIP1 protein binds axial filaments together.
Late nodules are precursors to chiasmata.
Only half the events at nodules result in cross-overs. Further information Staining of meiotic maize nuclei with antibodies against RAD51, the eucaryotic homologue of recA revealed structures reminiscent of nodules. Many of these structures, but not all, disappeared before pachytene. These observations also suggest that events leading to gene conversions are distinct from those leading to cross overs. Such a suggestion is inconsistent with molecular models of recombination.