scholarly journals Mutagenesis inEscherichia coli

1970 ◽  
Vol 15 (2) ◽  
pp. 147-156 ◽  
Author(s):  
B. A. Bridges ◽  
Rachel E. Dennis ◽  
R. J. Munson
Keyword(s):  
Dna Synthesis ◽  
Mutation Rate ◽  
Phage Genome ◽  
Multiplicity Of Infection ◽  
Mutation Process ◽  
Amber Mutation ◽  
Induced Mutation ◽  
Phage Dna ◽  
T4 Phage ◽  
Image Position

SUMMARYA system has been developed for the study of reversion of an amber mutation responsible for a deficiency in DNA synthesis in T4 phage E51. When complexed with bacteria able to suppress the amber mutation the induced mutation rate per phage genome per rad isWhen complexed with bacteria unable to suppress the amber mutation (and being thus unable to synthesize phage DNA) the induced mutation rate is at least 14 times lower indicating that DNA synthesis is necessary for the production of the majority of functional reversions at the amber site. The induced mutation rate in suppressor-containing bacteria is independent of multiplicity of infection between 0·2 and 5, suggesting that recombination immediately after irradiation between phage genomes is unlikely to be a requirement for the mutation process.

An amber mutation in the gene encoding the beta' subunit of Escherichia coli RNA polymerase

1982 ◽  
Vol 152 (2) ◽  
pp. 736-746
Author(s):  
S P Ridley ◽  
M P Oeschger
Keyword(s):  
Escherichia Coli ◽  
High Temperature ◽  
Rna Polymerase ◽  
Coli Strain ◽  
Beta Subunit ◽  
Temperature Sensitive ◽  
Amber Mutation ◽  
Gene Encoding ◽  
Amber Suppressor

An Escherichia coli strain carrying an amber mutation (UAG) in rpoC, the gene encoding the beta prime subunit of RNA polymerase, was isolated after mutagenesis with nitrosoguanidine. The mutation was moved into an unmutagenized strain carrying the supD43,74 allele, which encodes a temperature-sensitive su1 amber suppressor, and sue alleles, which enhance the efficiency of the suppressor. In this background, beta prime is not synthesized at high temperature. Suppression of the mutation by the non-temperature-sensitive amber suppressor su1+ yields a protein which is functional at all temperatures examined (30, 37, and 42 degrees C).

scholarly journals Kinds of mutations formed when a shuttle vector containing adducts of benzo[a]pyrene-7,8-diol-9,10-epoxide replicates in COS7 cells.

1987 ◽  
Vol 7 (3) ◽  
pp. 1267-1270 ◽  
Author(s):  
J L Yang ◽  
V M Maher ◽  
J J McCormick
Keyword(s):  
Gel Electrophoresis ◽  
Shuttle Vector ◽  
Point Mutations ◽  
Linear Increase ◽  
Amber Mutation ◽  
Large Deletions ◽  
Base Substitutions ◽  
Bound Residues ◽  
Supf Gene ◽  
Two Populations

We have investigated the kinds of mutations induced when a shuttle vector containing covalently bound residues of the (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) replicates in the monkey kidney cell line COS7. The target for detecting mutations was the 200-base pair gene for a tyrosine suppressor tRNA (supF), inserted at the EcoRI site in shuttle vector p3AC (Sarkar et al., Mol. Cell. Biol. 4:2227-2230, 1984). When introduced by transformation, a functioning supF gene in progeny plasmid recovered from COS7 cells allows suppression of a lacZ amber mutation in the indicator Escherichia coli host. Treatment of p3AC with BPDE caused a linear increase in the number of BPDE residues bound per plasmid. Untreated plasmids and plasmids containing 6.6 BPDE residues were transfected into COS7 cells, and the progeny were assayed for mutations in the supF gene. The frequency of mutants generated during replication of the BPDE-treated plasmids was not higher than that from untreated plasmids, but the two populations differed markedly in the kinds of mutations they contained. Gel electrophoresis analysis of the size alterations of 77 mutant plasmids obtained with untreated DNA and 45 obtained with BPDE-treated DNA showed that the majority of the mutant progeny of untreated plasmids exhibited gross alterations, principally large deletions. In contrast, the majority of the mutants generated during replication of the BPDE-treated plasmids contained only minor alterations, principally point mutations. Sequence analysis of progeny of untreated plasmids containing putative point mutations showed insertions and deletions of bases and a broad spectrum of base substitutions; in those from BPDE-treated plasmids, all base substitutions involved guanosine . cystosine pairs.

scholarly journals ASYMMETRIC EFFECTS OF DELETIONS AND SUBSTITUTIONS ON HIGH NEGATIVE INTERFERENCE IN COLIPHAGE LAMBDA

Genetics ◽  
1982 ◽  
Vol 102 (3) ◽  
pp. 299-317
Author(s):  
G J Vance Makin ◽  
W Szybalski ◽  
F R Blattner
Keyword(s):  
Double Point ◽  
Point Mutations ◽  
Strand Transfer ◽  
Amber Mutation ◽  
Negative Interference ◽  
Asymmetric Effects ◽  
Coliphage Lambda ◽  
Double Recombinant ◽  
Three Factor

ABSTRACT Experiments have been performed to help clarify the role of nonhomologies in phage λ recombination. Three-factor crosses were carried out, and the frequencies of single and double recombinants in the two adjoining intervals were compared when the central marker was either a double point mutation (v1v3) or deletion (rex-cI deletion) or nonhomologous substitution (imm434). In all cases the lefthand marker was a bio substitution (Fec- phenotype, which does not permit plating on recA  -), and the righthand marker was an amber mutation in gene O. Experiments were performed in all four possible arrangements of the central and rightward markers, while selecting for the Fec+ phenotype on the recA  - host. As anticipated, high negative interference (HNI) was observed with point mutations, but when the central marker was a substitution nonhomology, HNI was reduced about tenfold. Surprisingly, when the central marker was a simple deletion, a dramatic asymmetry in results was observed, with HNI being exhibited only when the central deletion marker was acquired by the double recombinant. These results indicate that under normal conditions (red  +, gam  +, rec  +) and with noninhibited DNA replication, recombination in coliphage λ entails a highly asymmetric step that could be at the level of strand transfer or mismatch repair.

scholarly journals ISOLATION AND CHARACTERIZATION OF AMBER SUPPRESSORS IN YEAST

Genetics ◽  
1976 ◽  
Vol 82 (2) ◽  
pp. 251-272
Author(s):  
Susan W Liebman ◽  
Fred Sherman ◽  
John W Stewart
Keyword(s):  
Amino Acids ◽  
Cytochrome C ◽  
Yeast Strain ◽  
Normal Amount ◽  
Amber Mutation ◽  
Genetic Analyses ◽  
Isolation And Characterization ◽  
And Function ◽  
Nonsense Suppressors

ABSTRACT Nonsense suppressors were obtained in a haploid yeast strain containing eight nutritional mutations, that are assumed to be amber or ochre, and the cyc1-179 amber mutation that has a UAG codon corresponding to position 9 in iso-1-cytochrome c. Previous studies established that the biosynthesis and function of iso-1-cytochrome c is compatible with replacements at position 9 of amino acids having widely different structures (Stewart and Sherman 1972). UV-induced revertants, selected on media requiring the reversion of one or two of the amber nutritional markers, were presumed to contain a suppressor if there was the unselected reversion of at least one other marker. The 1088 suppressors that were isolated could be divided into 78 phenotypic classes. Only 43 suppressors of three classes caused the production of more than 50% of the normal amount of iso-1-cytochrome c in the cyc1-179 strain. Genetic analyses indicated that all of these highly efficient amber suppressors are allelic to one or another of the eight suppressors which cause the insertion of tyrosine at ochre (UAA) codons (Gilmore, Stewart and Sherman 1971). Furthermore, only tyrosine has been identified at position 9 in iso-1-cytochrome cin cyc1-179 strains suppressed with these efficient amber suppressors.

scholarly journals NONSENSE MOTILITY MUTANTS IN SALMONELLA TYPHIMURIUM

Genetics ◽  
1973 ◽  
Vol 73 (2) ◽  
pp. 229-245
Author(s):  
Patricia S Vary ◽  
Bruce A D Stocker
Keyword(s):  
Salmonella Typhimurium ◽  
Structural Component ◽  
Phase 1 ◽  
Avoidance Reaction ◽  
Wild Type ◽  
Amber Mutation ◽  
Small Minority ◽  
Complementation Groups ◽  
Basal Apparatus ◽  
Derivatives Of

ABSTRACT Of 313 motility-deficient mutants isolated from an LT2 his(amber) strain fixed in phase 1 by gene vh2-, 25 regained motility when amber or ochre suppressors were introduced, in F' factors or by transduction. The fla mutants (23 amber, 1 ochre) fell in complementation groups A, B, C, F, K, a new group, M, and at least one further new group; the hypothesis of a fla gene which specifies only an RNA structural component of a flagellum-synthesizing basal apparatus is disproven for the corresponding genes. Hfr and transductional crosses confirmed gene assignments from complementation and indicated that flaM and another new fla locus map near H1. A small minority of motile bacteria were detectable in many of the amber fla mutants. In groups A and F some pairs of amber fla mutants complemented each other, and perhaps each of these groups corresponds to more than one structural gene. The suppressed derivatives of a mutant with an amber mutation in H1 made flagella morphologically and serologically indistinguishable from wild-type flagella. A slowspreading but flagellate mutant showed mainly non-translational motility in broth, and in a viscocs medium the bacteria reversed very frequently; its amber mutation, probably near H1, is inferred to cause a defect in chemotaxis, so that the bacteria give the avoidance reaction continuously.

Kinds of mutations formed when a shuttle vector containing adducts of benzo[a]pyrene-7,8-diol-9,10-epoxide replicates in COS7 cells

1987 ◽  
Vol 7 (3) ◽  
pp. 1267-1270
Author(s):  
J L Yang ◽  
V M Maher ◽  
J J McCormick
Keyword(s):  
Gel Electrophoresis ◽  
Shuttle Vector ◽  
Point Mutations ◽  
Linear Increase ◽  
Amber Mutation ◽  
Large Deletions ◽  
Base Substitutions ◽  
Bound Residues ◽  
Supf Gene ◽  
Two Populations

We have investigated the kinds of mutations induced when a shuttle vector containing covalently bound residues of the (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) replicates in the monkey kidney cell line COS7. The target for detecting mutations was the 200-base pair gene for a tyrosine suppressor tRNA (supF), inserted at the EcoRI site in shuttle vector p3AC (Sarkar et al., Mol. Cell. Biol. 4:2227-2230, 1984). When introduced by transformation, a functioning supF gene in progeny plasmid recovered from COS7 cells allows suppression of a lacZ amber mutation in the indicator Escherichia coli host. Treatment of p3AC with BPDE caused a linear increase in the number of BPDE residues bound per plasmid. Untreated plasmids and plasmids containing 6.6 BPDE residues were transfected into COS7 cells, and the progeny were assayed for mutations in the supF gene. The frequency of mutants generated during replication of the BPDE-treated plasmids was not higher than that from untreated plasmids, but the two populations differed markedly in the kinds of mutations they contained. Gel electrophoresis analysis of the size alterations of 77 mutant plasmids obtained with untreated DNA and 45 obtained with BPDE-treated DNA showed that the majority of the mutant progeny of untreated plasmids exhibited gross alterations, principally large deletions. In contrast, the majority of the mutants generated during replication of the BPDE-treated plasmids contained only minor alterations, principally point mutations. Sequence analysis of progeny of untreated plasmids containing putative point mutations showed insertions and deletions of bases and a broad spectrum of base substitutions; in those from BPDE-treated plasmids, all base substitutions involved guanosine . cystosine pairs.

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