'The beginning of diplotene is recognised by the dissolution of the synaptonemal complex and the tendency of the recombined homologous chromosomes of the bivalents to separate from each other except at the sites of crossovers. These X-shaped structures, are called chiasmata' . The text also states, 'In oocytes of some vertebrates, diplotene can last for months or years' . Thus, both statements are factually correct. However, the duration of the stage (Reason) does not explain the structural changes that characterize its beginning (Assertion).