Mouse, sheep and bovine metaphase II oocytes were briefly preincubated
in medium with 6-dimethylaminopurine (6-DMAP) and thereafter activate
d with ethanol before further culture in 6-DMAP supplemented medium. T
he presence of 6-DMAP enhances the efficiency of activation and the sp
eed of pronuclear formation but has no effect on DNA synthesis. These
results are discussed in the context of recently published data showin
g that the preincubation of condensed chromosomes with 6-DMAP blocks D
NA synthesis when nuclei become reformed.