Cytologic evidence for preferential inactivation of the paternally derived X chromosome in XX mouse blastocysts.
A total of 941 mouse blastocysts obtained from two types of crosses in which one of parents carried Cattanach's X/autosome translocation was studied cytogenetically by quinacrine mustard fluorescence. The rearranged X (Xt) and the normal X (Xh) were distinguished by size. Karyotype analysis was successful in 721 embryos, of which 205 were heterozygous for Cattanach's translocation. A single heterochromatic and brightly fluorescent X chromosome was identified in 154 metaphase spreads from 89 blastocysts consisting of 32--96 cells. The paternally derived X chromosome (Xp) was heterochromatic in 87% and 88% of the informative cells from the crosses XnXn x XtY and XtXn x XnY, respectively. This preferential choice of Xp at the blastocyst stage might have an important bearing upon the preponderance of cells with an inactive Xp in the chorion and yolk-sac splanchnopleure.
D000818:Animals; D001755:Blastocyst / Q000648:ultrastructure*; D002823:Chorion / Q000648:ultrastructure; D003433:Crosses, Genetic; D005260:Female; D005453:Fluorescence; D006570:Heterochromatin / Q000648:ultrastructure; D008677:Metaphase; D051379:Mice; D012730:Sex Chromosomes / Q000648:ultrastructure*; D014178:Translocation, Genetic; D014960:X Chromosome / Q000648:ultrastructure*; D015017:Yolk Sac / Q000648:ultrastructure
D006570:Heterochromatin