Nuclear-Cytoplasmic Interactions. The Basis for the Regulation of Gene Activity

Abstract

As suggested by Morgan (1937) differential activity of nuclei is caused by differences in cytoplasmic environment; therefore, the first step of differentiation depends upon the nature of the cytoplasm in various parts of the egg (Lehman, 1957; Briggs and King, 1959; Nikitina, 1964). Cytoplasm heterogeneity first appears during oogenesis as a result of the process designated ooplasmic segregation. The essence of this process is the formation of egg polarity and the animal-vegetative (and in many animals, dorsal-ventral as well) gradient distribution of active biological compounds such as RNA's, proteins, etc. The animal part of the egg is characterized by a higher level of metabolism (Brachet, 1960, 1961; Raven, 1964).