ANALYSIS OF RESTRICTION ENZYME-INDUCED CHROMOSOMAL-ABERRATIONS BY FLUORESCENCE IN-SITU HYBRIDIZATION

Fluorescence in situ hybridization and Giemsa staining of metaphase ch romosomes were used to determine the relative frequencies of symmetric exchange aberrations (translocations) and asymmetric exchange aberrat ions (rings, dicentrics, and polycentrics) after exposure of human lym phoblastoid cells to restriction enzymes or X-rays. The yield of symme tric exchanges was determined with the use of chromosome-specific prob es for human chromosomes 2 or 4, which were hybridized to metaphase ch romosomes from cells exposed to the enzymes PvuII, SacI, or XbaI or 3 or 5 Gy of X-rays. The yield of asymmetric exchanges was determined in Giemsa-stained metaphase chromosomes from the same enzyme-treated or irradiated cell population. About 1.5- to 3-fold more symmetric than a symmetric exchanges were induced after restriction enzyme treatment. H owever, after X-ray treatment the yield of dicentrics relative to the yield of reciprocal translocations was close to the expected 1:1 ratio . (C) 1993 Wiley-Liss, Inc.