ABSTRACT
Genes encoding guanine nucleotide-binding ras proteins have now been identified in all eukaryotic organisms examined, ranging from yeast to humans. These proteins display a high degree of evolutionary conservation, implicating ras in a fundamentally essential cellular role in all eukaryotes. The downstream effect(s) of ras in metazoans remains unclear, as does the extent of functional redundancy in organisms harboring more than one ras protein. The cellular slime mold Dictyostelium discoideum is one such organism. Two very similar ras genes with distinct patterns of expression have been identified, Dd ras and Dd rasG.
