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首页> 外文期刊>Journal of bacteriology >Cloning and physical mapping of the dnaA region of the Escherichia coli chromosome.
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Cloning and physical mapping of the dnaA region of the Escherichia coli chromosome.

机译：大肠杆菌染色体dnaA区的克隆和物理作图。

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The dnaA gene of Escherichia coli K-12, supposedly present in the deoxyribonucleic acid (DNA) of specialized transducing phase lambda i21 dnaA-2, was cloned onto plasmid pBR322. The new plasmid was named pMCR501. Physical analyses of DNAs of lambda i21 dnaA-2 and pMCR501 revealed the following. The lambda i21 dnaA-2 DNA retained the delta sr I lambda 1-2 and ninR5 deletions and imm21 substitution which were originally present in the parental phage. The size reduction was compensated for by the insertion-substitution segment (tna-dnaA region) in lambda i21 dnaA-2 DNA. The fractional size of this segment was approximately 7 megadaltons (Md), or 10 kilobases, which was found to be the sum of the tna insertion subsegment of ca. 3.5 Md and the dnaA substitution subsegment of ca. 3.5 Md. Phage P1-mediated transductional mapping between the dnaA46 and tna mutations gave a cotransduction frequency of 84%, corresponding to approximately 5 kilobases. Thus, it is strongly suggested that the dnaA gene resides in the lambda i21 dnaA-2 DNA. Cleavage mapping with the restriction endonuclease of pMCR501 DNA confirmed that it was constructed by excising a BamHI fragment of 4.29 Md, containing the 3.5-Md dnaA substitution segment, from the lambda i21 dnaA-2 DNA, inserting it into the sole BamHI cleavage site on pBR322.
机译：假定存在于专门的转导期λ21 dnaA-2的脱氧核糖核酸（DNA）中的大肠杆菌K-12的dnaA基因被克隆到质粒pBR322上。新质粒命名为pMCR501。对λi21 dnaA-2和pMCR501的DNA进行的物理分析显示以下内容。 λi21 dnaA-2 DNA保留了最初存在于亲本噬菌体中的δsr Iλ1-2和ninR5缺失和imm21取代。尺寸减小由λi21 dnaA-2 DNA中的插入取代片段（tna-dnaA区）补偿。该片段的分数大小约为7兆道尔顿（Md），或10千碱基，这是ca的tna插入子片段的总和。 3.5 Md和dnaA替代子片段。 3.5 dnaA46和tna突变之间的Md。噬菌体P1介导的转导作图给出了84％的共转导频率，相当于大约5个碱基。因此，强烈建议dnaA基因存在于λi21 dnaA-2 DNA中。用pMCR501 DNA的限制性核酸内切酶进行的切割图谱确定了它是通过从lambda i21 dnaA-2 DNA上切下一个包含3.5-Md dnaA取代片段的4.29 Md的BamHI片段而构建的，将其插入到唯一的BamHI切割位点上。 pBR322。

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