A commissure; especially, the optic commissure, or crucial union of the optic nerves
The cytologically visible consequence of a reciprocal recombination event in meiosis, observable in the later stage of meiotic prophase Chiasmata hold homologous chromosomes together prior to anaphase of the first meiotic division
A cross-shaped structure formed during crossing-over and visible during the diplonema stage of meiosis