What structure disappears during the diplotene phase of prophase I?

During the diplotene phase of prophase I of meiosis, the synaptonemal complex disappears. The synaptonemal complex is a protein structure that forms between homologous chromosomes during prophase I, aiding in the process of synapsis, which is the pairing of homologous chromosomes. This complex facilitates the exchange of genetic material through crossing over and helps ensure accurate chromosome segregation.

As the cell progresses through diplotene, the synaptonemal complex breaks down, allowing the paired homologous chromosomes to begin to separate slightly, although they are still held together at points called chiasmata where crossing over has occurred. The dissolution of the synaptonemal complex is crucial for the transition to the next stages of meiosis, as it marks a significant step towards the eventual segregation of homologous chromosomes.

While the chiasma is a critical structure that remains until later stages, as it represents the sites of crossing over, and the bivalent refers to the structure of a pair of homologous chromosomes, the synaptonemal complex specifically is what disappears during this phase. Purkinje fibers, related to cardiac muscle conduction, are not involved in meiosis and are therefore not relevant in this context.