Fig. 7. Estimate of the size of repair patch accompanied by A/C repair. Each mismatched or gapped substrate was incubated with RH95021 or Colo26 cell extract in the presence of [α-³²P]dGTP, recovered and digested with MluI. The relative mass corresponding to 3903 bp fragments was estimated using the Gel Doc 1000 system. Autoradiography of the same gel was performed using a PhosphorImager. From the relative mass and the radioactivity, the specific radioactivity in each band was calculated. The specific activity measurements of the 3903 bp fragments derived from G:C nick(+), GAP1 and GAP2 substrates were highly proportional to the number of guanine residues in the gaps. This linear relationship (R² = 1.00) was used to calculate the number of incorporated dGMP residues associated with each correction event. The repair patch size was estimated based on the local DNA sequence.