Expression analysis of p16 INK4a in cervical carcinomas by RT-PCR. Top, electrophoregram after Southern blot hybridization with the p16INK4a-specific radioactive probe. Middle and bottom, electrophoregrams after ethidium bromide staining. Middle, RT-PCR with viral E7 gene-specific primers as a control for E7 expression. Bottom, RT-PCR with the GAPDH-specific primers as a control for stability and concentration of RNA. T – carcinomas, N – normal tissue. Specimen numbers above the upper lines are as on fig. 1 and table 1.