Role of the Chromocenter in Nonrandom Meiotic Segregation of Nonhomologous Chromosomes inDrosophila melanogasterFemales

The evidence supporting universal significance of physical links between pericentromeric regions of homologous chromosomes for their bipolar orientation during the first meiotic division is discussed. The pericentromeric chiasmata between homologs or (in the absence of the latter) chromocentric links between nonhomologs, which are preserved until prometaphase, compensate for the disturbed binding between homologous pericentromeric regions in both structural or locus mutants. When the links between nonhomologs are involved, interchromosomal effects on chromosome disjunction and nonhomologous pairing were revealed by the genetic methods. An explanation suggested for genetic events observed during Drosophilameiosis conforms with the original, cytogenetically proved model of the orderly two-ring chromocenter formation and reorganization.