Diagram of exons 7 and 8 of the EpoR gene. The coding sequences are shown as solid boxes, the intervening sequences are depicted as lines, and the 3′ untranslated region as an open box. The lettered arrows indicate the position and orientation of the oligonucleotide primers described in the Materials and Methods. The open arrowhead (▿) above the mutant allele (bottom) indicates the position of the deletion. An Rsa I (R) restriction map of the 177-bp PCR amplification product using primer pair C and F is shown at the bottom.