= Synaptonemal complex
The <synaptonemal complex> is an organized <protein> scaffold assembled between aligned homologous <chromosomes> during <Prophase I> of <meiosis>. Two lateral elements run along the homologues, and transverse components connect them through a central region. Its zipper-like appearance makes <chromosome synapsis> visible, but the structure itself is not a completed exchange of <DNA>.
Yeast <mutants> lacking functional Zip1 helped separate these events. Homologues could pair, yet normal <synaptonemal complex> assembly failed and meiotic progression was disrupted. The comparison distinguishes initial recognition and alignment from construction of the full scaffold.<ZIP1 is a synaptonemal complex protein required for meiotic chromosome synapsis by M. Sym and others>[1993, abstract: pairing, defective complex formation and meiotic arrest]{ref} This is why a microscopy image showing nearby <chromosomes> should not automatically be interpreted as evidence for a completed <crossing over>.
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