What is Crossing over and what is Chiasma?
iNon-sister chromatids of paired homologous chromosomes at pachytene stage of 1st mejotic division break and rejoin with the pieces of the pairing parterns resulting genetic recombination. This is known as crossing over.
During diplotene stage as the homologous chromospomes move apart they remain attached to one another at specific points, termed chiasmata. Chiasma is the site on the chromosomes where crossing over had previously occured.