Autoradiographic Studies of X-chromosome Duplication in an XO/X-isochromosome X Mosaic Human Female

Inheritance of quantitative expression of erythrocyte glucose-6-phosphate dehydrogenase activity in the Negro?a twin study

“…Precedent perhaps exists for nonrandom X-inactivation. In cases where abnormal X-chromosomes have been studied using tritiated thymidine labeling techniques, the abnormal X-chromosome has been shown to be the late labeling (and sex chromatin forming) chromosome (Giannelli, 1963;Muldal et aL, 1963;Grumbach et aL, 1963;Miller et al, 1963;Atkins and Santesson, 1964;London et aL, 1964;Rowley et aL, 1964). This evidence supports the concept that a specific X-chromosome may be preferentially inactivated in a cell in contrast to purely random X-inactivation, although the data can also be explained by cell selection, with loss of the cells in which the abnormal X-chromosome is functional.…”

The Pattern of Dna Synthesis in the Chromosomes of Human Blood Cells

“…12). Morishima et al (10) reported that a structurally abnormal X was the late replicator in 100 per cent of cells observed. Similar findings have been reported by others (15,16).…”

“…Recent advances in the understanding of nucleic acid metabolism and in techniques for the handling of chromosomes make possible a combined study of chromosomal function and structure (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). The reproduction of somatic cell chromosomes is completed before the onset of cell division.…”

“…FIGURE10 DNA synthesis during the X through Z intervals has been labeled. Scattered small areas; extensive replication in the late X; a lesser degree in regions of the Nos.…”

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.…”