title: Sex and the single chromosome.
abstract: Just as homology can trigger a chain of events as described in many of the chapters of this volume, sometimes a lack of homology causes a crisis of a different sort. So it is for the single X chromosome in XY males in many species. Divergent sex chromosome pairs, such as the X and Y chromosomes in mammals and in fruit flies, are thought to have evolved from homologous autosomes. During evolution, the Y chromosome has retained little coding capacity, leaving the male with reduced gene dosage for many functions encoded by the X chromosome. In this chapter we focus on dosage compensation in Drosophila, in which most X-linked genes are upregulated by a male-specific ribonucleoprotein complex. This complex is thought to recognize the X chromosome through approximately 35 dispersed chromatin entry sites and then spread in cis to dosage compensate most genes on the X chromosome.
authors.affiliation: Department of Biology, Tufts University, Medford, Massachusetts 02155, USA.
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Meller
authors.forename: Mitzi I
authors.initials: MI
authors.lastname: Kuroda
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002843:Chromatin / Q000235:genetics; D004268:DNA-Binding Proteins; D004303:Dosage Compensation, Genetic; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics; D005260:Female; D008297:Male; D008322:Mammals / Q000235:genetics; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000235:genetics; D014176:Protein Biosynthesis; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C094166:msl-2 protein, Drosophila