Ontology of Biological Attributes entry OBA_2053155 (RRM2B/SMAD1 protein level ratio in blood) can be described as follows. A compound attribute that is the ratio of amount of ribonucleoside-diphosphate reductase subunit M2 B (human) in blood to amount of mothers against decapentaplegic homolog 1 (human) in blood. Also known as: the ratio of amount of ribonucleoside-diphosphate reductase subunit M2 B (human) in blood to amount of mothers against decapentaplegic homolog 1 (human) in blood.