Final answer:
During prophase I of meiosis, 4. recombination nodules appear along the synaptonemal complex where genetic material is exchanged between non-sister chromatids. These structures mark the points of crossover and mediate the process of genetic recombination, leading to genetic variation.
Step-by-step explanation:
During prophase I of meiosis, structures called recombination nodules appear along the synaptonemal complex where genetic material is exchanged between nonsister chromatids. These recombination nodules mark the points of crossover and mediate the process of genetic recombination. They facilitate the exchange of chromosomal segments, known as crossing over, which leads to genetic variation.