The fraction of DNA released on pulsed-field gel electrophoresis gels may differ significantly between genomes at low levels of double-strand breaks

A common way to use pulsed-field gel electrophoresis (PFGE) for measuring the induction and repair of DNA double-strand breaks (DSBs) in mammalian cells is by using the fraction of total DNA released, FR, from the plug. We have analyzed the general relationship between initial chromosome sizes and FR. It is shown that, because of the difference in initial chromosomal size, the discrepancy in FR values between human and rodent cells may become significant at doses of radiation producing approximately 5 DSBs/100 Mbp or less.