Author(s): Ajit Kumar Saxena , Divya Singh, Jyoti Gupta
In human five chromosomal loci encode ~ 360 copies ribosomal genes are called nucleolar organizer regions (NORs). These are located on the short arm of the acrocentric chromo-somes. The exact role of NORs is not known but it helps in the assembly of ribosomes during cell-division (mitosis). In the present case study the Down syndrome case used as model of non – disjunction event because of having an extra copy of acrocentric chromosome become imperative to know the associations between acrocentric chromosomes and NORs sites asso-ciated transcriptional event. In this case high incidence of NORs expression (>60% / cell) were observed. However, this study of NORs explores the mechanism of transcription dur-ing neuronal differentiation causes “mental retardation” has not been documented earlier in the literature.