Gaubatz J W
Department of Biochemistry, University of South Alabama College of Medicine, Mobile 36688.
Mutat Res. 1990 Sep-Nov;237(5-6):271-92. doi: 10.1016/0921-8734(90)90009-g.
The ability of eukaryotic organisms of the same genotype to vary in developmental pattern or in phenotype according to varying environmental conditions is frequently associated with changes in extrachromosomal circular DNA (eccDNA) sequences. Although variable in size, sequence complexity, and copy number, the best characterized of these eccDNAs contain sequences homologous to chromosomal DNA which indicates that they might arise from genetic rearrangements, such as homologous recombination. The abundance of repetitive sequence families in eccDNAs is consistent with the notion that tandem repeats and dispersed repetitive elements participate in intrachromosomal recombination events. There is also evidence that a fraction of this DNA has characteristics similar to retrotransposons. It has been suggested that eccDNAs could reflect altered patterns of gene expression or an instability of chromosomal sequences during development and aging. This article reviews some of the findings and concepts regarding eccDNAs and sequence plasticity in eukaryotic genomes.
相同基因型的真核生物根据环境条件的变化在发育模式或表型上发生变化的能力，常常与染色体外环状DNA（eccDNA）序列的改变有关。尽管这些eccDNA的大小、序列复杂性和拷贝数各不相同，但其中特征最明确的含有与染色体DNA同源的序列，这表明它们可能源于基因重排，如同源重组。eccDNA中丰富的重复序列家族与串联重复和分散重复元件参与染色体内重组事件的观点一致。也有证据表明，这类DNA的一部分具有类似于逆转座子的特征。有人提出，eccDNA可能反映了发育和衰老过程中基因表达模式的改变或染色体序列的不稳定性。本文综述了一些关于真核生物基因组中eccDNA和序列可塑性的研究发现和概念。
