Rapid human chromosome aberration analysis using fluorescence in situ hybridization

We have used in situ hybridization of repeat-sequence DNA probes, specific to the paracentromeric locus 1q12 and the telomeric locus 1p36, to fluorescently stain regions that flank human chromosome 1p. This procedure was used for fast detection of structural aberrations involving human chromosome 1p in two separate experiments. In one, human lymphocytes were irradiated with 0, 0·8, 1·6, 2·4 and 3·2 Gy of ¹³⁷Cs γrays. In the other, human lymphocytes were irradiated with 0, 0·09, 0·18, 2·0, 3·1 and 4·1 Gy of ⁶⁰Co γrays. The frequencies (per cell) of translocations and dicentrics with one breakpoint in 1p and one elsewhere in the genome were determined for cells irradiated at each dose point. These frequencies both increased with dose, D, in a linear-quadratic manner. The δ α and β coefficients resulting from a fit of the equation f(D) = δ + αD + βD² to the translocation frequency dose-response data were 0·0025, 0·0027 and 0·0037 for ¹³⁷Cs γrays, and 0·0010, 0·0041, and 0·0057 for ⁶⁰Co γrays. The δ α and β coefficients resulting from a fit to the dicentric frequency dose-response data were 0·0005, 0·0010 and 0·0028 for ¹³⁷Cs γrays and 0·0001, 0·0002 and 0·0035, for ⁶⁰Co γrays. Approximately 32,000 metaphase spreads were scored in this study. The average analysis rate was over two metaphase spreads per minute. However, an experienced analyst was able to find and score one metaphase spread every 10 s. The importance of this new cytogenetic analysis technique for biological dosimetry and in vivo risk assessment is discussed.