Heteromorphisms of Ag stained nucleolus organizer region [NORs] in acrocentric chromosomes of Egyptians

ABSTRACT

The nucleolar organizer region [NORs] of the acrocentric chromosomes of 80 normal Egyptians [40 males, 40 females] were studied using the Ag-staining technique [NSG]. The Ag-staining of NORs varied from one individual to the other, yet a consistent pattern of Ag +ve NORs was present in each individual. The modal number of Ag +ve NORs per cell ranged from 6 to 10. The average modal number of Ag +ve NORs per individual was 7.65. No sex difference was observed in the sample studied. The size distribution of silver +ve NORs revealed that very large NORs occurred with a frequency of 7%. The frequency of large NORs was 24.13%, medium sized NORs was 30.75%, small sized NORs was 14.62%, while the frequency of absent NORs was 23.5%. A racial difference in the expression as well as in the size of NORs is proposed. Only one individual [1.25%] was identified as possessing a double NORs [dNORs]