The Holliday junctions in homologous recombination are between identical or nearly identical sequences, leading to a symmetric arrangement of sequences around the central junction. This allows a branch migration process to occur where the strands move through the junction point. Cleavage, or resolution, of the Holliday junction can occur in two ways. Cleavage of the original set of strands leads to two molecules that may show gene conversion but not chromosomal crossover, while cleavage of the other set of two strands causes the resulting recombinant molecules to show crossover. All products, regardless of cleavage, are heteroduplexes in the region of Holliday junction migration.