X-Chromosome Dosage Compensation
نویسندگان
چکیده
The X and Y chromosomes of placental and marsupial mammals originated from a pair of autosomes. Ohno hypothesised nearly 50 years ago that the expression levels of X-linked genes should be doubled to compensate for the degeneration of their Y-linked homologues during sex chromosome evolution. The advent of microarray and RNA (ribonucleic acid) sequencing technologies in the past decade prompted a series of empirical tests of Ohno’s hypothesis. Surprisingly, X-chromosome dosage compensation is found to be largely absent in mammals. Studies of multiple independently evolved sex chromosome systems from a variety of species revealed a large variation in sex-chromosome dosage compensation, ranging from absence of compensation to complete compensation, although further scrutiny is required because of the high heterogeneities in expression data acquisition and analysis methods among studies. The lack of sex chromosome dosage compensation in at least some lineages has important implications for understanding gene expression evolution and sex chromosome evolution.
منابع مشابه
Dosage compensation of the Drosophila white gene requires both the X chromosome environment and multiple intragenic elements.
The X-linked white gene when transposed to autosomes retains only partial dosage compensation. One copy of the gene in males expresses more than one copy but less than two copies in females. When inserted in ectopic X chromosome sites, the mini-white gene of the CaspeR vector can be fully dosage compensated and can even achieve hyperdosage compensation, meaning that one copy in males gives more...
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In many organisms sexual fate is determined by a chromosome-based method which entails a difference in sex chromosome-linked gene dosage. Consequently, a gene regulatory mechanism called dosage compensation equalizes X-linked gene expression between the sexes. Dosage compensation initiates as cells transition from pluripotency to differentiation. In Caenorhabditis elegans, dosage compensation i...
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In many animals, males have one X and females have two X chromosomes. The difference in X chromosome dosage between the two sexes is compensated by mechanisms that regulate X chromosome transcription. Recent advances in genomic techniques have provided new insights into the molecular mechanisms of X chromosome dosage compensation. In this review, I summarize our current understanding of dosage ...
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