We have documented mortality and cancer incidence in the families of 67 patients with ataxia-telangiectasia and 48 patients with xeroderma pigmentosum resident in Britain. For both diseases, parents of patients are obligate hétérozygotes and grandparents have a probability of heterozygosity of 0.5. Fourteen ataxia-telangiectasia patients had died by June 30, 1986. This was a significant exces...

Bleomycin exposure evoked a specific sensitivity in five ataxia telangiectasia (AT) long-term lymphoblastoid cell lines when compared to lines derived from four normal individuals or three patients with xeroderma pigmentosum. At all concentrations tested or after each treatment regimen, statistically significant differences in viability and cytogenetic damage were obvious, with the AT cell line...

Heterokaryons between fibroblasts from patients with classical Xeroderma pigmentosum (X.P.) and fibroblasts from normal or heterozygous subjects have indicated that normal cells contain at least threeto fourfold the amount of 'X.P.-enzyme' necessary for maximal unscheduled DNA synthesis and that the reduced enzyme levels in heterozygotes can be detected using heterokaryons with a high ratio of ...

The repair of bleomycin-damaged DNA was examined in human fibroblasts isolated from patients having the disease xeroderma pigmentosum (XP). In normal fibroblasts, the appearance of low-molecular-weight DNA was observed in the presence of increasing amounts of the drug. The studies in XP fibroblasts produced results which differed from those obtained in normal cells in two ways. (a) Prelabeled X...

Crude extracts of normal human diploid fibroblasts and of human peripheral blood lymphocytes excise thymine dimers from purified ultraviolet-irradiated DNA, or from the DNA presumably present as chromatin in unfractionated cell-free preparations of cells that had been labeled with [3H]thymidine. Extracts of xeroderma pigmentosum cells from complementation groups A, C, and D also excise thymine ...