The pairing of homoeologous chromosomes (q.v.) in an allopolyploid (q.v.). Thus if the genetic composition of an alloploid is given by AABB, where AA represent the chromosomes derived from one parent species and BB the chromosomes derived from the other parent species, then during meiotic prophase, A undergoes allosyndetic pairing with B. Such pairing indicates that the A and B chromosomes have some segments that are homologous, presumably because the two parent species have a common ancestry. In the case of autosyndesis, A pairs only with A, and B with B. Segmental alloploids form both bivalents and multivalents during meiosis because of allosyndesis.
Subjects: Genetics and Genomics.