Variations in DNA concentrations significantly affect the reproducibility of RAPD fingerprint patterns.

The influence of the DNA concentration was tested using two different primers and nine DNA samples. Major modifications in the DNA banding pattern were apparent between successive dilutions. Such differences could be explained by concomitant changes in three different molecular conditions: the presence of perfect priming sites, the amplification of rare sites and the existence of mismatch annealing events. At low DNA concentrations (less than 1 pg/microliter), molecular events occurred at random and had a direct consequence on the reproducibility of RAPD profiles. At the appropriate DNA concentration (between 100 ng/microliters and 10 pg/microliters), reproducibility was adequate at a given concentration, but RAPD profiles differed from one dilution to another. These observations demonstrate the usefulness of the bis-benzimide method for quantification of DNA extracts.