During meiosis I, the stage characterized by the appearance of recombination nodules is:

Step-by-step solution

During the pachytene stage of prophase I in meiosis, the bivalent chromosomes clearly appear as tetrads. This stage is characterized by the appearance of recombination nodules, which are the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes. Crossing over is an enzyme-mediated process and the enzyme involved is called recombinase. Answer: Pachytene