DNA replication and pattern regulation in the imaginal wing disc of Drosophila

Imaginal disc cells of Drosophila undergo pattern regulation when part of a disc is removed by microsurgery. I have analyzed DNA replication in imaginal disc cells during pattern regulation using both pulse and chronic labeling with tritiated thymidine. Both types of experiments have shown a local increase in the fraction of labeled cells associated with pattern regulation. In addition I have found that when pattern regulation takes place during chronic thymidine labeling approximately 15% of the cells in a "regenerated" region are unlabeled. Thus DNA replication may not be required for respecification of "positional values" in imaginal disc cells. These results are consistent with patterning information being important in controlling cell growth during normal development.