engleski

Diversity of satellite DNAs in the bivalve mollusk Donax trunculus

Satellite DNAs are non-coding, tandemly repeated DNA sequences that comprise long arrays in the genome and are usually located within heterochromatic regions of chromosomes. Among marine invertebrates, satellite DNAs have so far been studied in only a couple of species including the mollusk Donax trunculus. In D. trunculus, five distinct satellite families have been described previously. They are all present in low number of copies (less than 1% of total genomic DNA) and are distinct in their monomer sequence although some families share oligonucletide motifs. We have discovered three new satellites resident within the D. trunculus genome. Even though they all share the same monomer length, only two satellites can be considered related, differing only by diagnostic point mutations, whereas the third one is dissimilar in its nucleotide sequence, GC content, and genomic abundance. These satellites are especially intriguing because of the apparent discrepancy in the level of their sequence homogeneity between the cloned subset and the entire genomic set of these satellite families. Such coexistence of highly homogenized but divergent satellite subgroups might indicate the presence of dynamic processes of satellite diversification within the genome.

repetitive sequences; heterochromatin; concerted evolution

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