title: BrDU-Giemsa labeling studies of satellite associations in parents of children with trisomy 21 or 13.
abstract: Studies on satellite association (SA) in parents of trisomy 21 offspring have not provided meaningful comparisons of SA frequencies since the latter was not expressed as a function of cell division number. We have used BrDU-labeling to compare SA frequencies in first and second division metaphases from lymphocytes of parents with either a trisomy 21 or trisomy 13 child and a control group. Parental origin of nondisjunction was determined in three of six families using quinacrine heteromorphisms. In the two cases of trisomy 13 determined, the errors occurred in maternal meiosis. BrDU-labeled metaphases were analyzed for SA frequency in four groups: A) parents contributing the extra chromosome; B) spouses of the parents in A; C) parents (nine) in whom the origin of a trisomy 13 or 21 was unknown; and D) healthy controls (five). The mean numbers of SAs/cell and of chromosomes/SA were not significantly different among the four groups for both first and second division cells. Sex and age showed no effect on SA frequency. There were significant decreases in mean numbers of SA/cell and chromosomes/SA in second-division cells (chromatids differentially stained) compared with first-division cells (chromatids undifferentiated). In second-division cells, two-chromosome SAs of all types showed random concordant and discordant alignment in each subject. The results from this BrDU-labeling approach provide no evidence that either quantitative or qualitative parameters of SA are directly related to a tendency of nondisjunction. They also show that acrocentric nondisjunction occurs in the presence of random chromatid alignment in SAs.
mesh_terms: D000367:Age Factors; D001973:Bromodeoxyuridine; D002478:Cells, Cultured; D002871:Chromosome Banding; D002882:Chromosomes, Human, Pair 13 / Q000648:ultrastructure*; D002891:Chromosomes, Human, Pair 21 / Q000648:ultrastructure*; D006801:Humans; D009630:Nondisjunction, Genetic; D011110:Polymorphism, Genetic; D012737:Sex Factors; D013194:Staining and Labeling; D014314:Trisomy
chemical_list: D001973:Bromodeoxyuridine