Tritiated Thymidine Incorporation in an Isochromosome for the Long Arm of the X Chromosome in Man

Somatic stigmata of Turner's syndrome in a patient with 46,XXq-.

“…In our studies, a late-replicating pattern was evident for the abnormal X chromosome in all of the cells suitable for analysis. Tritiated thymidine studies have also indicated late labelling ofthe abnormal X in cases of 46,XXp - (Atkins et al, 1965;Steinberger et al, 1966), 46,XXr (Rowley et al, 1964), and 46,XXqi (Jacobs et al, 1961;Giannelli, 1963;Muldal et al, 1963 X chromosome may best be explained by lack of viability of those cells in which the normal X chromosome is inactivated and the abnormal X chromosome remains active. The high incidence of XO found in studies of fetuses obtained from spontaneous abortion may indicate large-scale cell death due to non-viability of the cells in which the normal X has been inactivated (Bowen and Lee, 1969;Larson and Titus, 1970).…”

PCR-based detection of mosaicism in Turner syndrome patients

“…First, it has been shown that, in Turner syndrome patients, the second, structurally abnormal X chromosome is selectively inactivated (Muldal et al 1963) and will be selectively amplified. Moreover, even in patients with a 45,X/46,XX karyotype, the allele of the second X will be more efficiently amplified, since X chromosomes in 46,XX cells are randomly inactivated; therefore, both alleles will be equally amplified, even in the presence of a large excess of 45,X cells.…”

Two Human X-Autosome Translocations Identified by Autoradiography and Fluorescence

“…In virtually all cases of structurally abnormal X chromosomes, such as rings [36,37], deletions [38,39], and isochromosomes [40][41][42], the abnormal X is invariably the late-replicating element in females heterozygous for such rearrangements. These chromosomal abnormalities all involve the loss of some X-chromosomal material and would constitute a nullisomic condition for the deleted segment if the normal X chromosome were inactivated.…”