A structure-specific endonuclease that resolves Holliday junction (HJ) intermediates during genetic recombination. Cleaves 4-way DNA junctions introducing paired nicks in opposing strands, leaving a 5'-terminal phosphate and a 3'-terminal hydroxyl group that are ligated to produce recombinant products. Mediates chloroplast nucleoid segregation during chloroplast division. Endonucleolytic cleavage at a junction such as a reciprocal single-stranded crossover between two homologous DNA duplexes (Holliday junction). A number of isoforms are produced. Albino phenotype and decrease in cpDNA copy number. RNAi mutant displays chloroplasts with no chlorophyll and aberrant nucleoid morphology.