Fig. 10. Model for chromosome core assembly and maintenance. In wild-type meiotic prophase, cohesin proteins localize along the axes of pairs of sister chromatids. Cohesin complexes are brought together by C(2)M, resulting in the formation of visible chromosome cores that provide a scaffold for SC assembly. In the absence of ORD activity, cohesin SMC subunits still associate stably with chromosome arms and chromosome cores can assembly transiently, but are not maintained.