The Y Chromosomal Lampbrush Loops of Drosophila

Abstract

In 1961, Meyer, Hess and Beermann published a description of “phase-specific functional structures in spermatocyte nuclei of Drosophila melanogaster and their dependence on the Y chromosome”. This paper initiated extensive research work on the Drosophila Y chromosome, which is based on the discovery of lamp-brush loop-like structures in primary spermatocyte nuclei. These nuclear structures in spermatocytes of Drosophila proved to be a general phenomenon, at least in the genus Drosophila (Hess and Meyer 1963 b; Hess 1967). They were recognized, on the basis of studies on spermatocytes of Drosophila hydei, as lampbrush loop-like active genetic loci related to the male fertility factors, which reside in the Y chromosome (Meyer 1963; Hess and Meyer 1963 b). By cytogenetic means Hess (1965) established a chromosome map of the Y chromosome of Drosophila hydei (Fig. 1). According to this map, one of the lampbrush loop-forming genes is located in the short arm of the Y chromosome, while four others reside in the long arm. These lampbrush loops in the long arm are clustered in two regions, one close to the kinetochore and one close to the end of the long arm (Hess 1965 a). The Y chromosome, in addition, carries two nucleolus organizer regions, one at each end (Meyer and Hennig 1974 a; Hennig et al. 1975).