The Attraction between Homologous Chromosomes

Abstract

IT has been shown that the chromosomes of Datura (American Naturalist, vol. 56, pp. 339–346, 1922), Hyacinthus (Genetics, vol. 10, pp. 59–71, 1925) and Uvularia (Journal of Genetics, in press), for example, are combined side by side, and end to end, at the reduction division. If n is the haploid number of chromosomes, this finding of partners and conjugation of chromosomes points to the presence of 2n different attractions. (It is easily demonstrated in Uvularia that homologous ends of each chromosome are opposed, for the ends of the chromosomes differ in appearance.) This is confirmed by the formation of trivalents, quadiivalents, quinquevalents, etc., in triploid, tetraploid, and other plants with more than two homologous chormosomes; and also be the fact that none of the 12 chromosomes of the haploid Datura pair at the reduction division (Fig. 1). Such a number of attracting forces seems perhaps unexampled in physics.