RESUMEN
A gene of Proteus mirabilis that can substitute for functions of the recA gene of Escherichia coli has been cloned into the plasmid pBR322, using shotgun experiments. The recA-like gene (recAp.m.) has been localized by restriction mapping within a 1.5-Md PstI fragment that is a part of two cloned HindIII fragments of the chromosome of P. mirabilis. The restriction map of the recAp.m. gene differs from that of the recA gene of E. coli. Functionally, the recombinant plasmids containing the recAp.m. gene restore a nearly wild-type level of UV-resistance to several point and deletion mutants in the recA gene of E. coli.
Asunto(s)
Clonación Molecular , Genes , Proteus mirabilis/genética , Recombinación Genética , Mapeo Cromosómico , Enzimas de Restricción del ADN/metabolismo , ADN Bacteriano , Escherichia coli/genética , PlásmidosRESUMEN
The plasmid designated pAD1 was isolated from the cells of four variants of Bacillus brevis var. G.-B. The plasmid DNA has a molecular weight of about 47.1 x 10(6) daltons and contains 43.4 mole % G+C. The bulk of pAD1 DNA (96--98%) is associated with the fraction of chromosome DNA and membranes. Restriction endonucleases Sma I, Sal I and Bam HI cleaved the plasmid DNA into two, two and six fragments, respectively. The cleavage map of the pAD1 genome has been constructed for these three endonucleases. Restriction enzymes Eco RI, Hind III, Kpn I and Pst I hydrolized the plasmid DNA into 16, 21, 10 and 9 fragments, respectively. The presence of repeated sequences in the plasmid genome was shown based on pAD1 DNA cleavage by these endonucleases.
Asunto(s)
Bacillus/genética , ADN Bacteriano/aislamiento & purificación , Plásmidos , Centrifugación por Gradiente de Densidad , Enzimas de Restricción del ADN/metabolismo , Microscopía Electrónica , Peso Molecular , Mutación , Conformación de Ácido NucleicoRESUMEN
Non-glucosylated T4 DNA was digested with R.EcoRI and the resulting fragments covalently joined to lambda vectors. The genetic content of each lambda-T4 hybrid was determined by marker-rescue tests. The isolation of many recombinants containing partial-digestion products of T4 DNA provided the overlapping sequences necessary to order fragments within the T4 genome. The present analyses include parts of the "early" region between genes 42 and 46, and much of the "late" region between genes 50 and 29. T4 cytosine-DNA digested to completion by R.EcoRI was used to identify the fragments of DNA within the lambda-T4 recombinants. The T4 cytosine-DNA was also sensitive to R.HindIII and R.Xho but not to R.BamH1.
Asunto(s)
Mapeo Cromosómico , Colifagos/genética , ADN Recombinante , Genes Virales , Citosina/metabolismo , Enzimas de Restricción del ADN , ADN ViralRESUMEN
In vitro repair of single strand breaks in T4 and phage DNA caused by 32p decay was studied. Zone centrifugation procedure showed that polynucleotide kinase, ligase enzyme system failed to repair 32P-damages. It was found that damaged DNA contained gaps and could be repaired by DNA-polymerase I, polynucleotide ligase treatment.
