The purpose of this study is to test kidney donors and kidney transplant recipients for apolipoprotein L1 gene (called APOL1) variants (or forms of the gene) and to see how these may affect them. Genes control the traits that you inherit from your family such as your eye color or blood type. Variation or changes in genes can also put some people at risk for developing certain diseases. Previous research has shown that variation in the APOL1 gene can put people at higher risk for kidney disease. The purpose of this study is to test kidney donors and recipients for APOL1 gene variants to see how this gene may impact people who receive a kidney transplant and those who donated a kidney.