engleski

Characterization of a complex satellite DNA in the mollusc Donax trunculus : analysis of sequence variations and divergence

A highly repetitive sequence in the genomic DNA of the bivalve mollusc Donax trunculus (Dt) has been identified upon restriction with EcoRV. Cloning and sequence analysis unraveled the presence of two groups of monomer units which can be considered distinctive satellite subfamilies. Each subclas is distinguishable by the presence of 17 evenly spread diagnostic nucleotides (nt). The respective consensus sequences are 155 bp in length and differ by 11%, while relevant internal substructures were not observed. Shared mutations among variants appear either as single changes or in long stretches. This pattern may arise from gene conversion mechanisms acting at different levels, suche as the spread of nt sequences of a similar length to the monomer repeat itself, and the diffusion of short tracts a few bp long. Subfamilies might have evolved from the occasional amplification and spreading of a monomer variant effected by gene conversion events.

tandem repetition ; concerted evolution ; gene conversion ; wedged clam ; marine invertebrate

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