Disclosed are methods for detecting mammalian genes encoding proteins which can function in microorganisms, particularly yeast, to modify, complement, or suppress a genetic defect associated with an identifiable phenotypic alteration or characteristic in the microorganism. Disclosed also are mammalian DNA sequences cloned by the above method, as well as polypeptide products of the expression of the DNA sequences in procaryotic or eucaryotic host cells and antibody substances which are specifically immunoreactive with said expression products. More specifically, the present invention relates to methods for cloning mammalian genes which encode products which modify, complement or suppress a genetic defect in a biochemical pathway in which cAMP participates or in a biochemical pathway which is controlled, directly or indirectly, by a RAS-related protein, to products (RNA, proteins) encoded by the mammalian genes cloned in this manner, and to antibodies which can bind the encoded proteins.