Genetics of somatic mammalian cells. XIV. Genetic analysis in vitro of auxotrophic mutants

Genetic analysis has been carried out on auxotrophic mutants produced by treatment of Chinese hamster ovary and the Chinese hamster lung cells with mutagenic agents in vitro . Thirty‐six different mutants were subjected to complementation analysis and biochemical tests. The different mutations studied result in growth requirements for proline; glycine; glycine or folinic acid; adenine or several of its precursors; inositol; adenine plus thymidine; and glycine plus adenine plus thymidine. The mutants which require glycine fall into four different complementation classes while those requiring adenine or hypoxanthine form two different complementation classes. The biochemical blocks of the latter two classes both occur somewhere in the steps involved in conversion of 5‐phosphoribosyl‐1‐pyrophosphate to 5‐aminoimidazole 4‐carboxylic acid ribonucleotide. The auxotrophic mutants described exhibit all‐or‐none responses to their specific nutrilite supplements and are stable with respect to reversion. They involve alterations in ten different genes, and hence form a useful set of mutants for a variety of genetic studies. All the auxotrophies produced in a single exposure to a mutagen are due to single gene mutations, even when multiple nutritional requirements were produced. All the mutations studied are recessive.