Figure 1.

Sample D18S58 data. D18S58 data for six samples, run on two different standard gels, are shown. Samples A, B, and C are control individuals, who do not carry variable-mobility alleles. (Sample A is CEPH control 1347-2). Both of the gels were scored as follows (in bp): A (149/149), B (151/149), and C (149/145). Samples 1–3 are from individuals who carry one stable-mobility and one variable-mobility allele each. On gel 1, these samples were scored as follows (in bp): 1 (145/145), 2 (153/153), and 3 (149/149). On gel 2, they were scored (in bp) as 1 (152/145), 2 (153/152), and 3 (152/149). These three individuals were genotyped numerous times (see Table 1), and their D18S58 alleles were sequenced (see Table 2). Gel 1 shows an example of a case in which it is particularly likely that the variable-mobility allele simply did not amplify to a detectable level. Once on a standard gel (shown) and once on a formamide gel, sample 1 appeared homozygous for the 145 allele. The variable-mobility allele never appeared to be this small in samples 2 or 3, suggesting that, in this case, it simply did not amplify from sample 1. Whether the results for samples 2 and 3 on gel 1 are due to lack of detectable PCR of the variable-mobility allele or to comigration of the stable- and variable-mobility alleles cannot be determined.