J Mol Biol 135: 565-80 (1979)[80140511]
The 1.672 g/cm3 satellite DNA of Drosophila melanogaster was purified
by successive equilibrium centrifugations in a CsCl gradient, an
actinomycin D/CsCl gradient, and a netropsin sulfate/CsCl gradient.
The resulting DNA was homogeneous by the physical criteria of thermal
denaturation, renaturation kinetics and equilibrium banding in each
of the gradients listed above. In addition, the complementary strands
could be separated in an alkaline CsCl gradients. Despite this
rigorous purification procedure, nucleotide sequence analysis
indicates the presence of two different DNA species in this
satellite, poly[(A-A-T-A-T)/(T-T-A-T-A)] and poly
[(A-A-T-A-T-A-T)/(T-T-A-T-A-T-A)]. Further physical, chemical
and template properties of the isolated complementary strands
demonstrate that these two repeating sequences are not interspersed
with each other. This result has biological significance since
sequences of this particular satellite are known to be located
primarily on two different chromosomes, Y and 2. These results
further suggest that the sequence heterogeneity observed in satellite
DNA of higher eukaryotes may result from mixtures of very closely
related but molecularly homogeneous repeated sequences each
restricted to a particular chromosome or chromosommi region.
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