Bgl II digest of the 581-bp PCR product amplified from genomic DNA from six representative individuals. Lanes 1 and 2, homozygous 807T (high receptor density); lanes 3 and 4, heterozygous CT (intermediate receptor density); lanes 5 and 6, homozygous 807C (low receptor density). Lanes 7 and 8, cloned genomic DNA from individuals homozygous for 807C and 807T, respectively, serving as positive control. Lane 9, molecular weight markers.