Figure 3 Analysis of transcription product of mutant APOB minigene harbouring the c.4217−1G→T mutation in intron 25. RNA isolated from COS‐1 cells, transfected with wild‐type and mutant APOB minigenes, was reverse transcribed and the cDNA region spanning from the 3′‐end of exon 25 to the 5′‐end of exon 26 was amplified by polymerase chain reaction (PCR). Untransfected cells (lanes 1–3); DNA size marker (lane 4); apolipoprotein B (apoB) cDNA in cells transfected with wild‐type (lane 5) and mutant (lane 6) minigenes; PCR amplification of mutant (lane 7) and wild‐type (lane 8) minigenes; cDNA of neomycin resistance gene in cells transfected with mutant (lane 10) and wild‐type (lane 11) minigenes; “mock” reverse transcription‐PCR in cells transfected with mutant (lane 12) and wild‐type (lane 13) minigenes. “Mock” RT‐PCR, RT‐PCR performed without the addition of reverse transcriptase to the reaction mixture.