Potential cross-hybridization between related olfactory receptor probes. A1–A3, The section was hybridized by DIG-labeled MOR235-1 (red, A1) and FLU-labeled MOR236-1 (green, A2) probes. The two probes share 74% identity, and there was no cross-hybridization (A3). B1–B3, The section was hybridized by DIG-labeled MOR244-1 (red, B1) and FLU-labeled MOR244-2 (green, B2) probes. The two probes share 91% identity, and there was cross-hybridization (B3). Arrows mark stained cells.