Recombination assay

Recombinant assays have revolutionized pharmacology and now functional systems can be constructed with engineered levels of responsiveness (i.e., through difference in receptor levels or co-transfection of other proteins). 

Saccharomyces cerevisiae mitotic recombination assay OECD... 

Genetic Toxicology Saccharomyces cerevisiae, Mitotic Recombination Assay (Original Guideline, adopted 23 October 1986)... 

Genetic toxicology Saccharomyces cerevisiae, mitotic recombination assay 1986... 

The Saccharomyces cerevisiae mitotic recombination assay OECD TG 481 US-EPA OPPTS 870.5575 EU Annex V B.16... 

Positive results from the Saccharomyces cerevisiae mitotic recombination assay indicate that a substance induces DNA recombination in this test system, i.e., mitotic gene conversion (within a gene) and/or mitotic crossing-over (between a gene and its centromere). 

DNA repair. Polymerase-deficient, and thus DNA repair-deficient, E. coli has provided the basis for a test that depends on the fact that the growth of a deficient strain is inhibited more by a DNA-damaging agent than is that of a repair-competent strain. The recombinant assay using Bacillus subtilis is conducted in much the same way because recombinant deficient strains are more sensitive to DNA-damaging agents. 

Thioacetamide induced an increase in sex-linked recessive mutations in Drosophila. It was non-mutagenic in the SalmonellalAmes mutagenicity assay, and in the Escherichia coli recombination assay. Protein synthesis in mouse hepatoma (MH-134), but not in L-929 cells, was enhanced by adding thioacetamide. 

Genetic Toxicology Saacharomyces cerevisiae, Miotic Recombination Assay (original guideline, adopted Cctober 23, 1986)... 

Other microbial mutation, repair and recombination assays have also been used in chemical screening, however, the data base for carcinogenicity-mutagenicity correlation established with these in vitro test systems is relatively limited at this time.62-70 At present, the Ames Salmonella assay appears to be the most generally applicable screen for the detection of chemical mutagens. No other mutagenesis assay has been shown to respond to such a wide group of chemical types as the Salmonella mutants. 

Bacillus subtilis (recombination assay) MnClj Mn(N03), MnS04 Mn(CH3COO)2 KMn04 Inhibition of growth in recombination deficient mutant (Rec ) compared to wild type (Rec ) M45 (Rec) No data + + + + Nishioka 1975 N) X 5... 

Heavily chlorinated hydrocarbon carcinogens such as dieldrin, DDT, and carbon tetrachloride are not positive in either the Ames test, the E. coli polA test, or yeast mitotic recombination assay. The reason for the lack of positive results for these compounds in all of the microbial assays is not known but may be related to their highly lipophilic nature which may result in their entrapment in microbial cell wall membranes. 

Chlorpyrifos is not mutagenic, as judged by mitotic recombination assays, and did not increase sister chromatid exchange above background in tests with chick (Gallus spp.) embryos and Chinese hamster (Cricetus spp.) ovary cells. Chlorpyrifos altered serum cortisol and decreased thyroxine concentrations in sheep given oral doses of 12.5 mg chlor-pyrifos g BW twice weekly for 43 days, indicting a need for more research on the role of chlorpyrifos in hormone metabolism. 

Fig. 4. Charge recombination assay to determine whether QbH2 leaves the RC. Change in absorbance at 865 nm following 3 laser flashes in RCs starting with Q, 0 in the Qg site in the presence of 2 reduced cyt C2 and either a Qq pool (upper trace) or a Q10 pool (lower trace). After the first two flashes, was reduced by the cytc 2 faster than the time constant of the apparatus consequently, only small absorbance changes were observed. The charge recombination kinetics in the presence of a Qo pool (lower dashed line in b) ) corresponds to (see Eq. 4a). This proves that QgH2 leaves the RC.

Of the 22 C mutants, isolated as resistant to D-fucose, 18 mapped between C" mutant sites. C8 and C 70 mapped close to C5. Both failed to give any wild-type recombinants with C5, and based on the number of Ara recombinants assayed, it was estimated that C 8 and 070 are, respectively, less than 0.02 and 0.1 recombination unit away from C5. The position of other mutant sites 067, 02, 04, 070) as being within the C gene was verified by deletion mapping [14]. 

Jahnz, M., Schwille, P. An ultrasensitive site-specific DNA recombination assay based on dual-color fluorescence cross-correlation spectroscopy. Nucleic Acids Res. 33, e60 (2005)... 

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