title: The X chromosomes of mammals: karylogical homology as revealed by banding techniques.
abstract: A comparison of the Giemsa-banding patterns of the X chromosomes in various mammalian species including man indicates that two major bands (A and B), which are resistant to trypsin and urea-treatments, are always present irrespective of the gross morphology of the X chromosomes. This is true in all mammalian species with the "original or standard type" X chromosomes (5-6% of the haploid genome) thus far analyzed. In the unusually large-sized X chromosomes the extra chromosomal material may be due either to the addition of genetically inert constitutive heterochromatin or to an X-autosome translocation. In these X chromosomes two major bands are present in the actual X-chromosome segment. Our data on C and G band patterns also support Ohno's hypothesis that the mammalian X chromosome is extremely conservative in its genetic content, in spite of its cytogenetic variability.
mesh_terms: D000818:Animals; D006570:Heterochromatin; D006801:Humans; D007621:Karyotyping; D008322:Mammals; D012730:Sex Chromosomes; D013194:Staining and Labeling; D014178:Translocation, Genetic; D014357:Trypsin; D014508:Urea
chemical_list: D006570:Heterochromatin; D014508:Urea; D014357:Trypsin