Fig. 8. Discrete sizes of nascent DNAs in the absence of MCM3 or during inhibition of DNA replication by aphidicolin. The DNA replication products of MCM3-depleted extracts, or extracts treated with 15 µg/ml aphidicolin, were resolved by denaturing 8 M urea 6% acrylamide gel electrophoresis. Untreated samples (-), treated for 30 minutes at 37°C with 0.1 mg/ml RNase A (R), or with 1.3 U/ml DNase I, are shown for both MCM3-depleted or aphidicolin blocked extracts. (B) DNA replication was followed by [-³²P]dCTP incorporation. (C) The labeled DNA replication products from mock-depleted or MCM3-depleted egg extracts were separated by alkaline 2% agarose gel electrophoresis, which provides less resolution than acrylamide gel electrophoresis but gives better separation of the two populations of nascent DNAs. Incubation with (+) or without (-) -exonuclease (-exo) is shown.