PCR analysis of the der(4) and der(11) containing somatic cell hybrids. m is the pUC19/Hpa II molecular weight marker, H is normal human, M is mouse, 4 is the der(4) hybrid, and 11 is the der(11) hybrid. (A) NUP98 exon B PCR product digested withTaq I. Mouse and human NUP98 cDNA sequences are highly conserved and the exon B PCR also amplified mouse NUP98. The mouse and human exon B PCR products were distinguished by a TaqI restriction site, which is present in the mouse product but absent in the human product. (B) NUP98 exon C PCR product.