Correlation between the condensation state of rDNA and rRNA synthesis during Xenopus laevis oogenesis

Fluorescence microscopy observations show that the state of condensation of rDNA is correlated with rRNA synthetic activity during Xenopus laevis oogenesis. The rDNA-containing chromatin is condensed in Feulgen-positive granules during previtellogenesis, a period characterized by very low rRNA synthetic activity. The rDNA appears in a highly dispersed state in vitellogenic oocytes in which rRNA synthesis occurs at a very high rate.