Final answer:
The recombination nodule facilitates genetic recombination during prophase I of meiosis, where it initiates and mediates the process of crossing over between non-sister chromatids of homologous chromosomes, contributing to genetic diversity.
Step-by-step explanation:
A recombination nodule contains the enzymatic machinery necessary to break and rejoin chromatids of the homologous chromosomes. Recombination nodules are located at intervals along the synaptonemal complex, marking the points of chiasmata that facilitate genetic recombination between non-sister chromatids during prophase I of meiosis.
This process involves the cleaving of double-stranded DNA at each chromatid near the nodule, followed by modification of the cut ends, and finally, establishing a new connection between the non-sister chromatids. This exchange of genetic material, known as crossing over, contributes to genetic diversity by creating unique combinations of genes.
Following the crossover, the synaptonemal complex disassembles, leading to the condensation and separation of homologous pairs, which are then held together only by the chiasmata forming structures called tetrads. At least one chiasma per chromosome is essential for the proper separation of homologous chromosomes during meiosis I. The homologous recombination process repairs DNA breaks during normal recombination and also when DNA is damaged.