The pattern of inheritance of resistance to growth inhibitionby canavanine in Neurospora crassa is shown to result from interactionsbetween a major gene and several modifiers. The major gene controlsthe production of a constitutive enzyme that destroys canavanine. Themodifiers affect the rate of uptake of the analog from the medium.Strains which lack the enzyme activity are canavanine sensitive; strainswhich possess it are resistant, but the level of resistance is dependenton the rate of uptake.
The canavanine degrading enzyme was partially purified and itsproperties studied. The detoxification reaction was shown to be acleavage of canavanine yielding hydroxyguanidine.
