Hypothesis: Since Neurospora grows on minimal media, must have enzymes that convert simple compounds to amino acids necessary for growth
Neurospora species grow on a minimal medium containing sugar, inorganic salts and vitamin biotin
This means that they have metabolic pathways that makes proteins including enzymes
Neurospora species are all haploids
This means it is possible to study the expression of genes without worrying about dominance or recessive alleles.
Any mutations should be easy to detect since mutations will not be masked by another allele.
Irradiated a large number of Neurospora, and thereby produced some organisms with mutant genes
Mutation was linked to not being able to make the necessary amino acids
Tested all the amino acids, and found that the mutant grew with arginine
Some mutant spores could not grow without addition of specific amino acid---arginine
Arginine pathway is not a simple pathway, involves several different steps and several different enzymes
MOlecules are syntheized as a series of steps each catalyzed by an enzyme; see a final product only when every enzyme in the pathway is working properly.