Chromosomal basis of dosage compensation in Drosophila. VI. Transcription and replication in male X-chromosome of D. melanogaster after X-irradiation

Abstract

The three principal attributes of Drosophila polytene X-chromosome in male namely, increased wodth, high rate of RNA sythesis and faster DNA replication, are probably casually interdependent and related to genetic dosage compensation. (see Lakhotia and Mukherjee 1970). A direct demonstration of this relationship is not possible from studies on the normal glands. However, an approach in this direction may be made since under certain circumstances like X-irradiation of larvae, the width of male X is reduced to approximate that of the asynapsed X's of female nuclei (Lakhotia 1970a; Mukherjee et al 1968). In the present paper some aspects of the alterations induced in the transcriptive and replicative organization of the male X following X-irradiation of late third instar larvae D. melanogaster will be presented, a preliminary account having been presented eralier (Lakhotia 1971).