RT-PCR generation of mutant Rh cDNA from the 6 SDM K562 cell lines. PCR products of 1,497 bp were obtained from each monoclonal K562 line after reverse transcription of purified mRNA from each line. To confirm that the K562 line expressed the anticipated Rh mutant, PCR products were gel-purified and subjected to direct sequencing. All lines were found to express the expected mutant Rh mRNAs. The cE(loop6)D K562 line had been characterized in a previous study.9 NTC, no template control.