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首页> 外文期刊>Molecular and Cellular Biology >Does Ribosomal DNA Get Out of the Micronuclear Chromosome inParamecium tetraurelia by Means of a Rolling Circle?
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Does Ribosomal DNA Get Out of the Micronuclear Chromosome inParamecium tetraurelia by Means of a Rolling Circle?

机译：核糖体DNA是否会通过滚圈从四毛草履毛中脱离微核染色体？

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摘要

The macronuclear genes coding for rRNA (ribosomal DNA [rDNA]) ofParamecium tetraurelia, stock 51, are arranged in polymers consisting of units made up of a transcribed coding region and a nontranscribed spacer region. The whole macronuclear polymer ends with a portion of the spacer on either end followed by a telomere. Six kinds of macronuclear units, or genes, were mapped. Spacers were different, and transcribed regions were the same. These genes are found in markedly different numbers in the macronucleus. The most common gene shows two regions in the spacer where a sequence is followed by a direct repeat. The next most common gene is similar but shows a deletion plus a number of base pair substitutions. Although most cosmid clones contain only a single kind of gene, many contain more than one. These are thought to be produced by somatic crossing over. The four micronuclear genes that have been isolated consist of a single central transcribed region and portions of the spacer on either end. Sequencing indicates that the two ends of the molecule are partially redundant. While the spacer region at the right end of the macronuclear polymer is derived from the micronuclear spacer on the right, the spacer at the left end of the macronuclear polymer is derived from regions of the micronuclear spacer on both the right and the left. To account for this situation, a rolling-circle model for generation of the macronuclear rDNA from the micronuclear DNA is proposed.
机译：编码草履虫（股票51）的rRNA（核糖体DNA [rDNA]）的大核基因排列在聚合物中，该聚合物由转录的编码区和非转录的间隔区组成。整个大核聚合物在任一端都带有一部分间隔基，然后是端粒。映射了六种大核单位或基因。间隔物不同，转录区域相同。在大核中发现这些基因的数量明显不同。最常见的基因在间隔区中显示两个区域，在该区域中依次序列是直接重复。下一个最常见的基因是相似的，但显示出缺失加上许多碱基对取代。尽管大多数粘粒克隆仅包含一种基因，但许多包含一个以上的基因。这些被认为是通过体细胞交叉产生的。已分离的四个微核基因由一个中央转录区和任一端的部分间隔物组成。测序表明该分子的两个末端是部分冗余的。虽然大核聚合物右端的间隔物区域衍生自右侧的微核间隔物，但大核聚合物左端的间隔物衍生自右侧和左侧的微核间隔物的区域。为了解决这种情况，提出了一种从微核DNA生成大核rDNA的滚圆模型。

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