Quantitative abnormalities of PIG-A transcripts in TK-1⁻ and TK-14⁻. RNA was reverse transcribed with random primers and PIG-A and β-actin mRNA were amplified by PCR. During PCR, radiolabeled amplification products were removed after every three cycles, separated by electrophoresis in polyacrylamide gel, and visualized by autoradiography. The bands corresponding to PIG-A and β-actin are indicated. Left panel, TK-4⁺; center panel, TK-1⁻; right panel, TK-14⁻.