In the presence of aphidicolin, chromosome-associated DmMCM2 is retained for up to 3 hours after induction of S phase by cyclin E , apparently stabilizing the association of DmMCM2 with chromosomes. It is concluded that DNA replication is required for dissociation of DmMCM2 from chromosomes. Thus, mitosis is not required for oscillations in chromosome binding of MCMs and it is proposed that cycles of MCM-chromosome association normally occur in endocycles. There is maternal expression of dpa throughout oogenesis. Effects of Mutation or Deletion Homozygous mutant animals develop into third instar larvae of normal size but pupariation is slightly delayed.
Mutant animals die during pupal development.
No imaginal discs are found in larval animals and the CNS of mutant larvae is reduced in size. Presence of endoreplicating tissues such as the gut, fat body and polytene chromosomes suggests that dpa is required during mitotic but not during endoreplicating cell cycles. More cells are labeled with BrdU in stage 16 embryos than are normally found. Despite the ectopic labeling, mutant larvae show fewer ganglion mother cells surrounding putative neuroblasts. Trends in Biochem.