Prophase I of meiosis I is a complex phase divided into five substages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis . During the Pachytene stage, recombination nodules appear at the sites where crossing over occurs between non-sister chromatids of homologous chromosomes . The sources explicitly state that crossing over is an enzyme-mediated process, and the specific enzyme involved is called recombinase . This enzymatic activity leads to the recombination of genetic material, a process that is completed by the end of the pachytene stage . Understanding these specific meiotic events is a high-priority strategy for medical aspirants, as NCERT textbooks serve as the primary source for approximately 95% of NEET Biology questions .