DNA helicase required for crossover formation, complete synapsis of homologous chromosomes and bivalent formation during meiosis. Is specific to recombination events resulting in interference-sensitive crossovers (class I meiotic crossover) (PubMed:19470578, PubMed:19417775). Works cooperatively with ZIP4 to promote crossovers (PubMed:22393242). ATP + H2O = ADP + H(+) + phosphate Detected in punctuate foci onto the chromosomes in prophase I meiocytes. Complete loss of fertility due to defect in meiosis. Belongs to the helicase family. SKI2 subfamily.