Given that one copy of the Rag1 gene is sufficient to produce normal levels of lymphocytes [22], Rag1+/− mice were regarded as wild-type (WT) with respect to Rag1. Serial CBCs were obtained every other month to determine if the mice had developed evidence of MDS such as pancytopenia or dysplasia. The gene discussed is RAG1; the disease is myelodysplastic syndrome.