Low-molecular-weight DNA in blood plasma as an index of the influence of ionizing radiation.

Low-molecular-weight DNA (180 bp) appears in blood plasma of irradiated rats. Its amount correlates directly with the irradiation dose. The cloned low-molecular-weight DNA is enriched with G/C pairs (48% compared with 40% in the rodent genome). Computer search against EMBL data showed that the sequence of these clones is homologous to various genomic repetitive elements. The program for identification of nucleosome-positioning sequences in eukaryotic nuclear DNA has shown that low-molecular-weight DNA fragments are able to form rather sustainable nucleosomes and have some peculiarity. The difference in the composition of low-molecular-weight DNA isolated from blood plasma of rats after irradiation at doses of 8 and 100 Gy consisted of the change in the levels of two dinucleotides (CpG and CpT). The DNA in question originates from different types of cells.