Abstract
Mutations at the bwnA locus of D. discoideum resulted in drastically reduced levels of activity of the enzyme homogentisic acid oxidase. Apparently, the brown phenotype associated with these mutations results from the accumulation of an intermediate in the tyrosine degradative pathway, homogentisic acid, and its subsequent spontaneous oxidation. This knowledge is used to devise improved screening procedures potentially useful in the parasexual genetics system of this organism.