Figure 2 Analysis of the transcription product of the APOB minigene harbouring the c.904+4A→G mutation in intron 8. RNA isolated from COS‐1 cells, transfected with wild‐type and mutant APOB minigenes,was reverse transcribed and the exon 7–exon 10 region of apoB cDNA was amplified by polymerase chain reaction (PCR). Untransfected cells (lanes 1–3); DNA size marker (lane 4); apolipoprotein (apo)B cDNA in cells transfected with wild‐type (lane 5) and mutant (lane 6) minigenes; “mock” reverse transcription (RT)‐PCR in cells transfected with mutant (lane 7) and wild‐type (lane 9) minigenes; cDNA of neomycin resistance gene in cells transfected with mutant (lane 8) and wild‐type (lane 10) minigenes; PCR amplification of mutant and wild‐type minigenes (lanes 11 and 12). “Mock” RT‐PCR, RT‐PCR performed without the addition of reverse transcriptase to the reaction mixture.