Interpopulation variation in the satellite DNA from grasshoppers with B-chromosomes

When run on a CsCl gradient the DNA from individuals containing B-chromosomes reveals a satellite peak in addition to the main DNA peak found in individuals without B-chromosomes. This was shown in several populations of grasshoppers. This B-chromosome DNA contains 28% repeated and 72% unique sequences as determined by hydroxyapatite chromatography. This was shown to be the case in two of the populations. The really surprising observation was that the repeated nucleotide sequences of the B-chromosome DNA have no apparent homology in this single species of grasshopper. This was demonstrated by the lack of hybridisation between labelled C-RNA transcribed from one B-chromosome DNA and the DNA from the B-chromosome peak from another population. This lack of homology was also suggested by density differences between B-chromosome satellites in CsCl gradients. Furthermore, there was no sequence homology between the satellite (B-chromosome) DNA and the main peak (nuclear) DNA.