Previously isolated human placental cDNA clones represent a fusion of specific RNA sequences encoded by two genes: lysosomal chitobiase (CTB) and G-protein γ5 subunit (GNG5, Fisher and Aronson, 1992a, 1992b). Both genes have now been mapped to 1p by PCR analysis of somatic cell hybrids and further refined to 1p22 by fluorescence in situ hybridization (FISH) using a YAC clone that contains both the chitobiase and γ5 genes. © 1995 S. Karger AG, Basel.