Sequence arrangement of the 16S and 26S rRNA genes in the pathogenic haemoflagellate Leishmania donovani.
Sequence arrangement of the 16S and 26S rRNA genes in the pathogenic haemoflagellate Leishmania donovani.
复制标题
致病性血鞭毛虫杜氏利什曼原虫中 16S 和 26S rRNA 基因的序列排列。
作者：
W. Leon;D. Fouts;J. Manning
动力学和化学分析表明，多诺瓦利什曼原虫的单倍体基因组有4.6 ~ 6.5 × 10(7) Kb对DNA。Cot分析表明，该基因组包含12%的快速再关联DNA， U3%的中重复DNA（平均重复频率为77次）和62%的单拷贝DNA。饱和杂交实验表明，rRNA编码序列占据了细胞核DNA的0.82%。这些序列的平均重复频率为166。沉降速度研究表明，两种主要rRNA的沉降值分别为26S和16S。利用基因32-溴化乙锭技术制备的rRNA:DNA杂交体的结构检查，确定了rRNA基因及其间隔序列在纯化rDNA长链上的排列。观察到长DNA链包含多个基因集（16S + 26S）。一个重复单元按给定顺序包含以下序列：(a)长度为2.12 Kb的16S基因，(b)长度为1.23 Kb的内部转录间隔段（Spl），其中包含一个可能编码5.8S rRNA的短序列，(C)长度为4.31 Kb的26S基因，包含一个长度为0.581 Ib的内部间隙区，(d)平均长度为5.85 Kb的外部间隔段。
Kinetic and chemical analysis show that the haploid genome of Leishmania donovani has between 4.6 and 6.5 X 10(7) Kb pairs of DNA. Cot analysis shows that the genome contains 12% rapidly reassociating DNA, U3% middle repetitive DNA with an average reiteration frequency of 77 and 62% single copy DNA. Saturation hybridization experiments show that 0.82% of the nuclear DNA is occupied by rRNA coding sequences. The average repetition frequency of these sequences is determined to be 166. Sedimentation velocity studies indicate the two major rRNA species have sedimentation values of 26S and 16S, respectively. The arrangement of the rRNA genes and their spacer sequences on long strands of purified rDNA has been determined by the examination of the structure of rRNA:DNA hybrids prepared for electron microscopy by the gene 32-ethidium bromide technique. Long DNA strands are observed to contain several gene sets (16S + 26S). One repeat unit contains the following sequences in the order given: (a) A 16S gene of length 2.12 Kb, (b) An internal transcribed spacer (Spl) of length 1.23 Kb, which contains a short sequence that may code for a 5.8S rRNA, (C) 26S gene with a length of 4.31 Kb which contains an internal gap region of length 0.581 Ib, (d) An external spacer of average length 5.85 Kb.