To solve this problem, we need to determine at which stage of meiosis the enzyme recombinase is required.$\newline$Let's analyze the stages of meiosis:$\newline \bullet$Zygotene: This is the stage where homologous chromosomes begin to pair up in a process called synapsis.$\newline \bullet$Pachytene: During this stage, homologous chromosomes are fully synapsed, and crossing over occurs.$\newline$ - Crossing over is facilitated by the enzyme recombinase, which helps in the exchange of genetic material between homologous chromosomes.$\newline \bullet$Diplotene: This stage is characterized by the separation of homologous chromosomes, except at the chiasmata where crossing over has occurred.$\newline \bullet$Diakinesis: This is the final stage of prophase I, where chromosomes condense further and prepare for metaphase I.$\newline$From the analysis, it is clear that recombinase is required during the pachytene stage for crossing over.$\newline$Therefore, the correct option is Option 1: Pachytene.