Cytogenetic Assays. In: D.J. Kirkland (Ed.) Statistical Evaluation of Mutagenicity Test Data. UKEMS Sub-Committee on Guidelines for Mutagenicity Testing. Report, Part III. Cambridge University Press, Cambridge, New York, Port Chester, Melbourne, Sydney, p. 184-232.
B.13/14. MUTAGENICITY: REVERSE MUTATION TEST USING BACTERIA
1. METHOD
This method is a replicate of the OECD TG 471, Bacterial Reverse Mutation Test (1997).
1.1. INTRODUCTION
The bacterial reverse mutation test uses amino-acid requiring strains of
Salmonella typhimurium
and
Escherichia coli
to detect point mutations, which involve substitution, addition or deletion of one or a few DNA base pairs (1)(2)(3). The principle of this bacterial reverse mutation test is that it detects mutations, which revert mutations present in the test strains and restore the functional capability of the bacteria to synthesise an essential amino acid. The revertant bacteria are detected by their ability to grow in the absence of the amino-acid required by the parent test strain.
Point mutations are the cause of many human genetic diseases and there is substantial evidence that point mutations in oncogenes and tumour-suppressor genes of somatic cells are involved in tumour formation in humans and experimental animals. The bacterial reverse mutation test is rapid, inexpensive and relatively easy to perform. Many of the test strains have several features that make them more sensitive for the detection of mutations including responsive DNA sequences at the reversion sites, increased cell permeability to large molecules and elimination of DNA repair systems or enhancement of error-prone DNA repair processes. The specificity of the test strains can provide some useful information on the types of mutations that are induced by genotoxic agents. A very large data base of results for a wide variety of structures is available for bacterial reverse mutation tests and well-established methodologies have been developed for testing chemicals with different physico-chemical properties, including volatile compounds.
See also General introduction Part B.
1.2. DEFINITIONS
A reverse mutation test
in either
Salmonella typhimurium
or
Escherichia coli
detects mutation in an amino-acid requiring strain (histidine or tryptophan, respectively) to produce a strain independent of an outside supply of amino-acid.
Base pair substitution mutagens
are agents that cause a base change in DNA. In a reversion test this change may occur at the site of the original mutation, or at a second site in the bacterial genome.
Frameshift mutagens
are agents that cause the addition or deletion of one or more base pairs in the DNA, thus changing the reading frame in the RNA.
1.3. INITIAL CONSIDERATIONS
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