According to the National Human Genome Research Institute, '''bone marrow transplantation''' is "a medical procedure to replenish the soft tissue within [[bone]]s that produces new [[blood cell]]s. Bone marrow transplants are necessary when marrow has been destroyed by drug or [[radiation therapy]] for [[cancer]], often [[leukemia]]. A bone marrow donor is usually a close relative of the patient."<ref>http://www.genome.gov/glossary.cfm?key=bone%20marrow%20transplantation</ref>