Evolution of Tribolium madens (Insecta,Coleoptera) Satellite DNA Through DNA Inversion and Insertion |
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Authors: | ?urdica Ugarkovi? Sonja Durajlija Miroslav Plohl |
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Institution: | (1) Department of Molecular Genetics, Ruder Bošković Institute, Bijenička 54, P.O. Box 1016, 41000 Zagreb, Croatia |
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Abstract: | Two different satellite DNAs from tenebrionid speciesTribolium madens (Insecta, Coleoptera) have been detected, cloned, and sequenced. Satellite I comprises 30% of the genome; it has a monomer
size of 225 by and a high A + T content of 74%. Satellite 11, with a monomer size of 711 by and A + T content of 70%, is less
abundant, making 4% of the total DNA. Sequence variability of the monomers relative to consensus sequence is 4.1% and 1.2%
for satellite I and II, respectively. Both satellites are localized in the heterochromatic regions of all chromosomes. A search
for internal motifs showed that both satellites contain a related subsequences, about 100 by long. The creation of satellite
I monomer is explained by duplication of the basic subunit, followed by subsequent divergence by single point mutations, deletions,
and gene conversion. Inversion of the subsequence in addition to its duplication has occurred in satellite II. The result
of this inversion is possible formation of a long, stable dyad structure. The 408-bp sequence, inserted within satellite II
monomer, shares no similarity with a basic subunit. Frequent direct repeats found within the inserted sequence point to its
evolution by duplication of shorter motifs. It is proposed that both satellites have been derived from a common ancestral
sequence whose duplication played a major role in the formation of satellite I monomer, while insertion of a new sequence
together with inversion of an ancestral one induced the occurrence of satellite II.
Correspondence to: D. Ugarković |
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Keywords: | Dyad structure Repetitive sequences Gene conversion Recombination Heterochromatin |
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