Ugarković D, Durajlija S, Plohl M
Department of Molecular Genetics, Ruder Bosković Institute, P.O. Box 1016, Bijenicka 54, 41000 Zagreb, Croatia.
J Mol Evol. 1996 Mar;42(3):350-8.
Two different satellite DNAs from tenebrionid species Tribolium madens (Insecta, Coleoptera) 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. 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 bp 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.
在黄粉虫（昆虫纲，鞘翅目）中检测到了两种不同的卫星DNA，并对其进行了克隆和测序。卫星I占基因组的30%；其单体大小为225 bp，A+T含量高达74%。卫星II的单体大小为711 bp，A+T含量为70%，含量较少，占总DNA的4%。卫星I和卫星II的单体相对于共有序列的序列变异性分别为4.1%和1.2%。两种卫星均定位于所有染色体的异染色质区域。对内部基序的搜索表明，两种卫星都包含一个约100 bp长的相关子序列。卫星I单体的产生是由基本亚基的重复，随后通过单点突变、缺失和基因转换发生分歧来解释的。卫星II除了重复外还发生了子序列的倒位。这种倒位的结果可能是形成了一个长的、稳定的二分体结构。插入卫星II单体内部的408 bp序列与基本亚基没有相似性。在插入序列中发现的频繁直接重复表明其通过较短基序的重复而进化。有人提出，两种卫星都起源于一个共同的祖先序列，其重复在卫星I单体的形成中起主要作用，而新序列的插入以及祖先序列的倒位导致了卫星II的出现。
