Ribosomal RNA genes (rDNA)
Ribosomal 18S-25S RNA Genes
The hybridization signals of the probe for the 18S-25S RNA genes were always located at the terminal position of the nucleolus-organizing regions (NOR) of the short arms of chromosome A and K and the long arm of chromosome I. The loci of the 18S-25S rDNA are situated in the segments Ap2, Iq3 und Kp2
Hybridization signal and condensation of rDNA
Direct detection with FITC-dUTP
Interphase and meiosis
In order to confirm the number of 3 chromosomes with 18S-25S rDNA loci also interphase nuclei and chromosomes in meiosis studied by FISH. As expected 6 FISH signals were observed on interphase nuclei and 3 signals on chromosomes in TelophaseII (haploid chromosome number).
Genes of the ribosomal 5S RNA
The probe for 5S rDNA showed hybridization signals in the cHC of the NO-Chromosomes I and K. On Chromosome I the 5S rDNA locus is situated on the distal part of the cHC on the long arm in position Iq12. The second 5S rDNA locus was found on chromosome K at about the middle of the cHC of the long arm, the position of the weak DAPI band named Kq25. The co-localization with the 18S-25S and the 5S rDNA probe confirm that the loci of both rDNA types are found on chromosomes I and K.