A cDNA clone coding for human protein kinase CK1 (casein kinase 1) has been isolated and sequenced demonstrating that it corresponds to a homolog of the CK1 alpha form found in bovine brain. The derived amino acid sequence of the human CK1 alpha is identical to the bovine counterpart except that it contains 12 extra amino acids at the carboxyl end. Using this cDNA sequence and PCR amplification, YAC genomic clones that contain this human CK1 alpha sequence have been isolated. These YACs have been used for fluorescent in situ hybridization in order to localize the human CK1 alpha gene to chromosome 13q13.