© 1977 by The Society for Integrative and Comparative Biology
Dosage Compensation: Transcription-Level Regulation of X-Linked Genes in Drosophila
Department of Zoology and Genetics Curriculum, University of North Carolina Chapel Hill, North Carolina 27514
In Drosophila melanogaster, the level of X-linked gene products is found to be equivalent in normal males and females (dosage compensation) and in metafemales (3X;2A); it is also equivalent in triploid females, intersexes (2X;3A) and metamales (XY;3A). In all instances, the expression of X-linked genes is regulated in such a fashion that it is concordant with the level of autosomal gene activity. This means that at least five different transcriptional levels exist for X-linked structural genes; the lowest in metafemales, the highest in metamales, and three different intermediate levels, in females (diploid or triploid), intersexes and males. Two models have been proposed for the regulatory mechanism. These models are discussed and current experimental approaches are reviewed.