Cytological Evidence for the Association of the Short Arms of the X and Y Chromosomes in the Human Male

Abstract

EVIDENCE for the association of the X and Y chromosomes during the first meiotic division in man has been documented^1,2. Until the centromere positions of the meiotic chromosomes were located with certainty, no information about the arm relationship between the two sex chromosomes could be obtained. The identification of the positions of the centromere in human male meiotic chromosomes at the late diplotene stage has been reported³. This observation revealed that the short arm of the Y chromosome was in association with the short arm of the X chromosome. Partial support for this finding was presented by Pearson and Bobrow⁴, who interpreted fluorescent staining of the distal end of the long arm of the Y chromosome of the XY bivalent in man as evidence that the short arm of the Y chromosome was associated with the X chromosome. Because the centromere position of the X chromosome could not be demonstrated in their material, it was not possible to determine which arm of the X chromosome was associated with the short arm of the Y chromosome. The purpose of this communication is to provide additional cytological evidence for the association of the X and Y chromosomes at their short arms.