Growth of yeast strain AH109 containing the genes indicated (AtGβ1γ1 alone or AtGβ1γ1 and phosducin) on yeast dropout media. Media missing tryptophan (-W) selects for the AtGβ1γ1 vector, resulting in positive growth for both genotypes. Media missing leucine (-L) selects for the phosducin vector, resulting in no growth for the strain lacking phosducin and positive growth for the strain containing phosducin. Media missing leucine, tryptophan, and histidine (-LWH) selects for a positive interaction between the two genes, resulting in no growth for the strain containing AtGβ1γ1 alone and positive growth for the strain containing both AtGβ1γ1 and phosducin. The latter growth indicates that the two genes physically interact.