Cytological demonstration of the helical structure of giant chromosomes

Alverdes(1) as long ago as 1912 interpreted the bands of the giant chromosomes found by Balbiani(2) in Chironomus as the result of spiralization. Later, Kaufmann,(3) applying plant-chromosome techniques to Drosophila giant chromosomes, concluded that the discoid or discontinuous appearance of these chromosomes was an expression of inadequate technique and that a spiral structure was the more accurate. Nevertheless, the discontinuous structure appeared to fit genetic data more easily.