HOMOLOGOUS CHROMOSOME PAIRING REMAINS AN UNSOLVED PROBLEM: A TEST OF A POPULAR HYPOTHESIS UTILIZING MAIZE MEIOSIS

A recently proposed and popular model for the mechanism of meiotic homologue pairing relies on prior association of nonhomologous chromosome arms of most similar length. According to this model, the diploid complement is organized into two genomic linear chains, each containing the various heterologues in the same sequence. At meiosis, then, appression of the two genomic chains could presumably readily accomplish homologue pairing. This model fails in its simplest form when observations of meiotic pairing of homologues in heterozygotes for arm length alterations are compared with computer-simulated predictions of the model. Contrary to predictions of the model, heterozygotes for arm length changes were found to exhibit only small frequencies of homologue-pairing failure, and this only for a single homologue pair in each case. It is difficult to conceive of a reasonable modification of this model that would be consistent with the observations.