DNA fork displacement rates in human cells.

DNA fork displacement rates were measured in 20 human cell lines by a bromodeoxyuridine-313 nm photolysis technique. Cell lines included representatives of normal diploid, Fanconi's anemia, ataxia telangiectases, xeroderma pigmentosum, trisomy-21 and several transformed lines. The average value for all the cell lines was 0.53 0.08 mum/min. The average value for individual cell lines, however, displayed a 30% variation. Less than 10% of variation in the fork displacement rate appears to be due to the experimental technique; the remainder is probably due to true variation among the cell types and to culture conditions.