Abstract
The Ag stainability of the nucleolus organizer region (NOR) was studied in the acrocentric chromosomes identified by Q banding of cultured lymphocytes in 41 karyotypically normal persons (33 males and 8 females) originating from southeast Estonia. The data obtained are compared with those established earlier for a combined Vienna-Ulm population of 51 karyotypically normal persons (see Mikelsaar et al., 1977a). Significant differences between the two populations in the frequency and patterns of Ag-positive NORs were found. The following findings were most striking: the frequency of Ag-positive NORs in chromosome 14 and in the totals was significantly lower in the Estonian population than in the Vienna-Ulm population (PPP<0.05) lower in chromosome 22 than in 13,15, and 21, but not 14.