Low rates of homogenization of the DBC-150 satellite DNA family restricted to a single pair of microchromosomes in species from the Drosophila buzzatii cluster

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Abstract
A satellite DNA family, termed DBC-150, comprises slightly GC-rich repeat units of approximately 150 bp that were isolated (by DNA digestions or PCR) from the genome of all seven Drosophila species from the buzzatii cluster (repleta group). The presence of subrepeats suggests that part of the extant DBC-150 monomer originated by the duplication of small sequence motifs. The DBC-150 family is compared to the previously described pBuM satDNA family, an abundant component of the genome of five species of the cluster. The two families are different in several aspects, including primary structure, A+T content, intraspecific and interspecific variability and rates of homogenization (or nucleotide spread). The data indicate a lower rate of homogenization (and absence of complete concerted evolution) of the DBC-150 compared to the pBuM family. FISH on metaphase chromosomes revealed that the DBC-150 family is located exclusively in the microchromosomes. To our knowledge this is the first record of a complex Drosophila satDNA restricted to a single pair of microchromosomes. The observed low rates of homogenization of the DBC-150 family might be related to a presumed reduction or suppression of meiotic recombination in the microchromosomes.