Methods and compositions comprising single guide RNAs targeted to an endogenous mammalian β globin gene (HBB), gamma globin gene (HBG1), B-cell lymphoma/leukemia 11A (BCL11A) gene, Kruppel-like factor 1 (KLF1) gene, CCR5 gene, CXCR4 gene, PPP1R12C (AAVS1) gene, hypoxanthine phosphoribosyltransferase (HPRT) gene, albumin gene, Factor VIII gene, Factor IX gene, Leucine-rich repeat kinase 2 (LRRK2) gene, Hungtingin (Htt) gene, rhodopsin (RHO) gene, Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, surfactant protein B gene (SFTPB), T-cell receptor alpha (TRAC) gene, T-cell receptor beta (TRBC) gene, programmed cell death 1 (PD1) gene, Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) gene, human leukocyte antigen (HLA) A gene, a LMP7 gene, a Transporter associated with Antigen Processing (TAP) gene, tapasin gene (TAPBP), a class II major histocompatibility complex transactivator (CIITA) gene, a dystrophin gene (DMD), a glucocorticoid receptor gene (GR), IL2RG gene or RFX5 for genetic alteration of cells are provided.