The fragments used in this experiment are about 300 base pairs long. The ordinate gives the relative optical density, the abscissa the log cot, i.e. the concentration x time, c_o being the concentration of single strands at the time t = 0. These values have been used to calculate the fractions of repetitive, moderately (intermediately = i) repetitive and nonrepetitive sequences given as violet, pink, and red curve in the lower part of the illustration (according to M. G. MURRAY et al., 1978).