LABORATORY DATA biochemical markers metabolic defect chromosomal assignment chromosome X localization chromosome Xq localization chromosome Xq27 localization chromosomal disorders chromosomal fragility, instability, breakage chromosome breakage syndromes foetal-amniotic biochemical data hypoxanthine-guanine phpsphoribosyltransferase defect (foetal) gene, structural-functional anomalies gene ana...

When the corneal epithelium of the Chinese hamster is irradiated with ionizing radiation in vivo, a rectilinear relationship is observed between the yield of chromosome aberrations and the dose of x-rays within a dose range of 10 to 150 r. There is no threshold effect for chromosome breakage down to the 10-r level. The mean breakage rate of 0.00352 breaks per cell per roentgen is in very close ...

We have utilized a dihydrofolate reductase (DHFR) probe in combination with selected probes from other positions along the 2q chromosome arm in a two-color fluorescence in situ hybridization analysis of early DHFR gene amplification events in CHO cells. These studies show clearly that the most frequent initiating event is the formation of a giant inverted duplication, resulting from chromosome ...

The En/Spm transposable element system in maize includes the functional element, En/Spm and the receptor element I/dSpm. An En receptor has been found that shows En-induced breakage. This En-responsive receptor (designated I836518) is located on the short arm of chromosome 9, proximal to Wx. In the presence of En, markers distal to the receptor show a loss of gene expression. Kernels heterozygo...

The Fanconi anaemia (FA) nuclear complex (composed of the FA proteins A, C, G and F) is essential for protection against chromosome breakage. It activates the downstream protein FANCD2 by monoubiquitylation; this then forges an association with the BRCA1 protein at sites of DNA damage. Here we show that the recently identified FANCE protein is part of this nuclear complex, binding both FANCC an...

Nijmegen breakage syndrome is a rare autosomal recessive genetic disease belonging to a group of disorders often called chromosome instability syndromes. In addition to a characteristic facial appearance and microcephaly, patients suffering from Nijmegen breakage syndrome have a range of symptoms including radiosensitivity, immunodeficiency, increased cancer risk and growth retardation. The und...

The B chromosome of maize has been used in a study of dicentric chromosomes. TB-9Sb is a translocation between the B and chromosome 9. The B-9 of TB-9Sb carries 60% of the short arm of 9. For construction of dicentrics, a modified B-9 chromosome was used, B-9-Dp9. It consists of the B-9 chromosome plus a duplicated 9S region attached to the distal end. In meiosis, fold-back pairing and crossing...

Ten long-term survivors of childhood acute lymphoblastic leukemia were studied to determine if cytogenetic abnormalities were present in lymphocytes following discontinuation of therapy. The study included patients diagnosed between 1969 and 1974 who had received radiation therapy and a minimum of 3 years systemic chemotherapy. At study, the patients had been off all therapy from 1.3 to 6.5 yea...

Chromosome breaks and hence chromosomal rearrangements often occur in maize stocks harboring transposable elements (TEs), yet it is not clear what types of TE structures promote breakage. We have shown previously that chromosomes containing a complex transposon structure consisting of an Ac (Activator) element closely linked in direct orientation to a terminally deleted or fractured Ac (fAc) el...