Function: Meiosis-specific component of some cohesin complex. Probably required during early meiosis for separation of sister chromatids and homologous chromosomes. Replaces RAD21 in premeiotic S phase (during early stages of prophase I), while RAD21 reappears in later stages of prophase I. May be involved in synapsis initiation and crossover recombination between homologous chromosomes. Subunit structure: Component of some meiotic cohesin complex composed of the SMC1 (SMC1A or SMC1B) and SMC3 heterodimer attached via their hinge domain, RAD21L which link them, and STAG3. Sequence similarities Belongs to the rad21 family.