Exontrap analysis of a fragment of genomic DNA encompassing exons 5 to 7 of GPIIb. A fragment of genomic DNA encompassing exons 5 to 7 of GPIIb from the proband and a control were cloned in the expression vector pET01 and transfected into CHO cells as described in Materials and Methods. RT-PCR analysis of RNA from the transfected cells yielded a fragment of 471 bp in the control and a product of 548 bp and a second smaller, less represented product of 481 bp in cells transfected with DNA from the [IVS5(+2)C→A]-GPIIb allele of the proband. Sequencing of the amplification products demonstrated that the 471-bp fragment comprised exons 5 to 7 of GPIIb and the vector exons, the 548-bp fragment is the result of insertion of intron 5 into the normal sequence, and the 481-bp product has intron 5 inserted and exon 7 partially deleted.