Differential termination of primer extension analysis of peripheral blood reticulocyte RNA from a normal subject or from 2 β15 carriers.

(A) Illustration of the principle underlying the experiment. The end-labeled (represented by *) 17-mer oligonucleotide (underlined sequence), described in “Materials and methods,” was hybridized to the mRNA, and reverse transcription was performed in the absence of dTTP. Products of 31 and 20 nucleotides resulted from the extension of normal and mutant (β15) alleles, respectively. Arrows represent the site of differential termination of primer extension. (B) Representative autoradiograph of PAGE separation of normal cDNA (lane 1), and cDNA from 2 β15 carriers (lanes 2 and 3, respectively). Lane 4 contains an end-labeled 17-nucleotide primer as a size marker. The position of the full-length primer extension product is on the right. The average ratio of mutated versus normal allele expression, using results from 2 independent experiments, is indicated at the bottom.