 Plants such as "Zea mays", "Arabidopsis thaliana" and "Tradescantia" have been used in various test assays for mutagenecity of chemicals.Mammalian cell lines such as Chinese hamster V79 cells, Chinese hamster ovary (CHO) cells or mouse lymphoma cells may be used to test for mutagenesis.Such systems include the HPRT assay for resistance to 8-azaguanine or 6-thioguanine, and ouabain-resistance (OUA) assay.