Abstract: The present disclosure provides a method of modifying a globin gene in the genome of a hematopoietic stem/progenitor cell (HSPC), the method comprising: A) obtaining HSPCs from an individual having a globin gene comprising a sickle cell disease (SCD)-associated single nucleotide polymorphism (SNP) to generate an in vitro population of CD34+ HSPCs and B) contacting the in vitro population with a genome editing composition, as described in further detail below. Also provided is a method of treating sickle cell disease (SCD) in an individual including administering to an individual an in vitro mixed population derived from the method of modifying a globin gene, as well as kits for practicing the same.