Ras proteins bind GDP/GTP and possess intrinsic GTPase activity.Defects in KRAS are a cause of acute myelogenous leukemia (AML). AML is a malignant disease in which hematopoietic precursors are arrested in an early stage of development. Defects in KRAS are a cause of juvenile myelomonocytic leukemia (JMML). JMML is a pediatric myelodysplastic syndrome that constitutes approximately 30% of childhood cases of myelodysplastic syndrome (MDS) and 2% of leukemia. It is characterized by leukocytosis with tissue infiltration and in vitro hypersensitivity of myeloid progenitors to granulocyte-macrophage colony stimulating factor. Defects in KRAS are the cause of Noonan syndrome type 3 (NS3). Defects in KRAS are a cause of gastric cancer (GASC).