The Biochemistry of Genetic Factors

Part VI. Mechanisms of resistance to metabolite analogues with anticancer activity

“…Numerous examples of enzyme deletion can now be defined in biologic systems as diverse as microorganisms and humans. 57,80 Heritable resistance to certain purine and pyrimidine analogues appears to arise in some bacteria and experimental neoplasms by genetically controlled alteration of specific enzymes which catalyze formation of nucleotide derivatives of these analogues. Such alterations are sometimes so drastic that enzyme activity is lost.…”

Biochemistry of Cancer

“…For modification of the cell's heredity by new elements that interact with the chromosome and replicate with cell proliferation, the best models can probably be found in work with bacterial systems ; from this it has become apparent that various kinds of subcellular particles can function as possible replication units and carriers of heritable information (11,18,19). The cur rent trend in thinking is illustrated by the concept of episomes, as discussed by Jacob and co-workers (6, 14,20).…”

Studies on a Temperature-sensitive Irreparable Mutant of <i>Neurospora Crassa</i>

“…Mutants of microorganisms which do not grow on the minimal medium have been obtained by many investigators and used for the study of genetics and biochemistry (Beadle 1957, Fincham 1959 . These mutants -biochemical or nutritional mutantsinclude those which require amino acids, vitamins, purines, pyrimidines, and/or some other growth factors.…”