Sister chromatids are not bivalent and therefore cannot form tetrads. The synaptonemal complex is the fusion of the sister chromatids at the start of Meiosis I. If two chromosomes have similar positions, structures, and origins they are referred to as sister chromatids. Syanpsis is the fusion of chromosomes at the start of Meiosis I. A chiasma (or chiasmata) is the place where crossing over occurs. Crossing over is an event that occurs in Meiosis II and results in the exchange of genetic information between sister chromatids. 1) True 2) False