The X chromosome of monotremes shares a highly conserved region with the eutherian and marsupial X chromosomes despite the absence of X chromosome inactivation. |
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| Authors: | J M Watson J A Spencer A D Riggs J A Graves |
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| Affiliation: | Department of Genetics and Human Variation, La Trobe University, Bundoora, Victoria, Australia. |
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| Abstract: | Eight genes, located on the long arm of the human X chromosome and present on the marsupial X chromosome, were mapped by in situ hybridization to the chromosomes of the platypus Ornithorhynchus anatinus, one of the three species of monotreme mammals. All were located on the X chromosome. We conclude that the long arm of the human X chromosome represents a highly conserved region that formed part of the X chromosome in a mammalian ancestor at least 150 million years ago. Since three of these genes are located on the long arm of the platypus X chromosome, which is G-band homologous to the Y chromosome and apparently exempt from X chromosome inactivation, the conservation of this region has evidently not depended on isolation by X-Y chromosome differentiation and X chromosome inactivation. |
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