Correlation of the nucleolar organizer and the fibrillar center of the nucleolus

The review is dedicated to the question, to what extent it is possible to speak about the correspondence of the fibrillar center (FC) of the nucleolus to the nucleolar organizer region (NOR) of the metaphase chromosome. The analysis of the literature on the problem provides grounds for the affirmation that the chromatin-containing elements of the FC and of the fibrillar component of the nucleolus correspond to the NOR. At the same time, the number of facts evidence in favour of the hypothesis that the FC serves as a kind of "depot" for nucleolar proteins. The latter makes it possible to consider the FC to be polyfunctional.