Pairing of homologous chromosomes (synapsis) commences at one or several points on the chromosome and is clearly seen during PACHYTENE of meiosis I.

• 同源染色体两两成对平行靠拢，这一现象也称联会，联会发生在染色体的一点或多点上，可以在减数第一次分裂的粗线期观察到。