Detection by microfluorography (rapid scintillation autoradiography) of twin spots derived from double strand DNA breaks.

In order to investigate the chemically or physically produced double strand DNA scissions, we have tried to detect 3•L-termini of the lesions. The termini were detected by an enzymic assay using 3H-TTP and terminal deoxynucleotidyl transferase, followed by rapid scintillation autoradiography. This enzyme is generally used for adding complementary homopolymer to vector and cDNA in recombinant DNA technology. As the result, exogenous nucleotides are additionable at random to 3'-hydroxy termini of both singleand double-strand DNA without any templet strand1). In the present study, barley nuclei were isolated from dry seed embryos2) . The nuclear suspension was dropped on a coverglass which was previously coated with a thin layer of gelatin, and the specimens were dried fairly at the room temperature. Then, the dried samples were ex-