engleski

Evolution of Tribolium madens (Insecta, Coleoptera) satellite DNA through DNA inversion and insertion

Two different satellite DNAs from tenebrionid species Tribolium madens have been detected, cloned and sequenced. Satellite I comprises 30% of the genome ; it has a monomer size of 225 bp and a high A+T content of 74%. Satellite II, with a monomer size of 711 bp and A+T content of 70% is less abundant making 4% of the total DNA. A search for internal motifs showed that both satellites contain related susequences about 100 bp long. The creation of satellite I monomer is explained by duplication of the basic subunit, followed by subsquence divergence by single point mutations, deletions and gene conversion. Inversion of the subsequence in addition to its duplication has occurred in satellite II. The 408 bp sequence, incerted within satellite II monomer shares no similarity with a basic subunit. It is proposed that both satellites have been derived from a common ancestral sequence whose duplication played a major role in the formation of the satellite I, while insertion of a new sequence together with inversion of an ancestral one induced the occurrence of satellite II.

dyad structure ; gene conversion ; recombination ; heterochromatin

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