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Biomedical subjects

J R Roth

Publications and source records attributed to J R Roth.

139 records · Page 8Linked to original sources
PubMed1970

UGA nonsense mutations in Salmonella typhimurium.

Salmonella typhimurium strain LT-2 carries a weak UGA suppressor activity. This activity prevents the detection of some UGA mutants as auxotrophs and probably accounts for the rarity of his UGA mutants in this strain. A selection method is described which permits the isolation of these rare his UGA mutants. Map distribution of his UGA mutations is normal, and their polarity effects are indistinguishable from the polarity effects of amber and ochre mutations at similar locations. Isolation and properties of a prototrophic his UGA mutant are described. UGA mutants are common among lac mutants isolated from Salmonella strains carrying an F'lac episome. Apparently the suppressor activity is insufficient to prevent detection of lac UGA mutants. It is not yet clear whether the suppressor activity plays an important role in normal cell physiology.

Chromosome Mapping↗
PubMed1968

Histidine and aromatic permeases of Salmonella typhimurim.

Mutants defective either in the histidine permease (hisP) or in the aromatic permease (aroP) were isolated in Salmonella typhimurium and were characterized. The hisP locus had a 49% linkage to purF by phage transduction. The aroP locus was close to proA. Merozygotes diploid for the hisP gene were constructed by episomal transfer, and hisP(+) was dominant over hisP. The properties of merozygotes are described and discussed. A method for the selection of revertants of hisP mutants was devised. By this method, one of the hisP mutants was characterized as an amber mutant. The specificity of the aromatic permease was investigated by using as substrates analogues of the aromatic amino acids and of histidine.

Carbon Isotopes↗