Variable number of tandem repeat (VNTR) polymorphism at locus D17S5 (YNZ22) in four ethnically defined human...

We have analyzed the hypervariable locus D17S5 in four well-defined human populations (Kachari of Northeast India; Dogrib Indian of Canada; New Guinea Highlander of Papua New Guinea; and a relatively homogeneous Caucasian population of North German extraction) using both Southern blot analysis and the polymerase chain reaction (PCR) technique to: (1) compare the efficiency and limitation of Southern blotting versus PCR-based techniques in genotyping variable number of tandem repeat loci, and (2) provide allele frequency data at this locus in these four anthropologically defined populations. Preferential PCR amplification of smaller alleles associated with D17S5 was corrected by lowering the DNA template concentration to 200 ng, and by reducing the extension time to 2 min. A perfect correspondence was observed between the results from Southern blot and PCR analysis in all but one sample. A very large allele, of approximately 24 to 25 repeat units, detected by Southern blotting, could not be amplified by PCR, resulting in an incorrect genotyping rate of less than 0.5%. Considering the grave consequences of mistyping in forensic and paternity testing, it is suggested that heterozygous controls consisting of large and small alleles should be employed in each PCR experiment, and PCR-generated homozygotes should be confirmed by Southern blotting. Significant variation in the number and frequency of alleles at this locus was observed in the four examined populations. A total of 15 different alleles were detected. The average heterozygosity varied from 54% in the Dogrib to 89% in the Kachari. No heterozygote deficiency was observed at this locus in any of the examined populations.