sickle-cell disease affects primarily people with sub sahara africa, the caribbean, mexico, africa, europe, india, asia. and it may be combined with other hemoglobinopathies as well. such as beta and alpha, in which those particular side effects and complications could be even more compounding and devastat g devastating. >> does that present a greater challenge when it comes to finding donors? >> right. it really does. i think in the african-american population we do have to understand that maybe we won't -- we do not have a large number of families with whole siblings. so that limits the actual availability for the donor, and that brings to light the gene therapy, where you don't necessarily need a donor for establishing a cure for bone marrow transplant. where they're taking a virus and implanting that virus with the normal hemoglobin-producing gene to then just produce normal hemoglobin. >> we know there have been challenges finding, getting african-americans to donate organs. is it easier to convince a patient, a donor, to give bone marrow? >> right. so -- >> than an organ? >> i think