Phenomenon that two homologous chromosomes exchange pieces of DNA during meiosis. The chance of a crossing-over is smaller as the genes (loci) are positioned closer to each other on the chromosome. A crossing-over will lead to two recombinant chromosomes; the recombinant chromosome then contains properties of both the father plant and the mother plant. If crossing-over occurs once during meiosis it is called a single crossing-over. In the event it happens twice it is called double crossing-over.
ST: coupling phase ↔ repulsion phase
BT: recombination