Gene expression analyses indicated that both the rag2:Myc and rag2:Myc + rag2:prl-3 leukemias expressed the lymphocyte specific genes rag1 and rag2 and the T-cell genes lck and tcrB, but not B-cell related genes igD or igM, indicating all leukemias generated were of T-cell origin. The gene discussed is RAG1; the disease is leukemia.