Homologous chromosomes synapse and crossing over occurs.

Prophase I of meiosis I

Explanation:

Zygotene stage of prophase I of meiosis I include the pairing of homologous chromosomes assisted by the synaptonemal complex. The homologous chromosomes are paired and appear as tetrads. A zygotene is followed by the pachytene stage of prophase I during which the paired homologous chromosomes exchange some part of the genetic segments.

This process is called crossing over and generate new gene combinations that were otherwise not present in the parent cell. The paired homologous chromosomes start separating during the diplotene stage of prophase I but remain paired at the point of crossing over. These points are not called chiasmata.

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this protocol provides a detailed procedure for co-immunoprecipitation (co-ip) to identify protein–protein interactions.