Anomalous Sex Chromosome Systems

  • T. C. Hsu
Part of the Heidelberg Science Library book series (HSL)

Abstract

Modern cytological investigations have firmly established the conclusion that in mammals the male is always heterogametic, or has an XX/XY sex determination system. Many earlier reports of XO males prove to be erroneous. The sizes of the X and the Y may vary considerably, but rarely are the two morphologically indistinguishable. Ohno et al. (1964) concluded that the X chromosome of the eutherian mammals constitutes approximately 5% of the genome, regardless of the diploid number. In species with numerous autosomes (such as the dog), the X may be the longest element. In species with low diploid numbers, such as many bats, the X may be among the shortest elements. Exceptional cases occur when the X chromosome carries a large amount of constitutive heterochromatin, such as the Chinese hamster and the European field vole Microtus agrestis. As far as the functional protion (euchromatin) of the X chromosome is concerned, the genetic content of the X in relation to the entire genome is remarkably constant.

Keywords

Germinal Peru Eutherian Mammal Protion 

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Copyright information

© Springer-Verlag New York Inc. 1979

Authors and Affiliations

  • T. C. Hsu
    • 1
  1. 1.Section of Cell Biology, M. D. Anderson Hospital and Tumor Institute Texas Medical CenterThe University of Texas System Cancer CenterHoustonUSA

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