For this we employed the Rag-1-Cre knockin allele, which was reported to recombine floxed genes with very high efficiency at the CLP stage.46, 47 Lymphoma onset was slightly delayed in the Eμ-Myc;Rag-1-Cre mice compared with the Eμ-Myc control animals. The gene discussed is MYC; the disease is lymphoma.