Chiasmata

From EvoWiki

A chiasma, related to the Greek word for "cross", is the technical term for the point where two chromatids are intertwined. The chiasmata are thought to be the points where two nonsister chromatids exchange genetic material during meiosis. The chiasmata become visible during the Diplonema Stage of meiosis, but the actual "crossing-over" of genetic material is thought to occur during the previous Pachytene Stage. When tetrads, which are composed of two pairs of sister chromatids, begin to split the only points of contact are at the chiasmata.