Chiasma pattern in a carrier of a 13; 14 Robertsonian translocation. Trivalents containing either two chiasmata on one arm together with two chiasmata on the other (arrow, top) or two chiasmata on both arms (arrow, bottom) and two additional examples (cut outs, middle). Note the dicentric nature of this metacentric derivative 13; 14 Robertsonian translocation, as illustrated by the drawings (middle). These chiasma patterns of the trivalents in this carrier are similar to those of the individual chromosomes 13 and 14 in human males with normal karyotypes. Revised from  and .