Tri-allelic patterns at the D7S820 locus detected in two generations of a Chinese family.

Alleles at the D7S820 STR locus have 6-14 different numbers of a four-nucleotide (GATA) repeat motif arranged in tandem. The D7S820 tri-allelic pattern is rare and has not been reported in the Chinese population. In this study we report a three-banded pattern at the D7S820 locus observed in a Chinese family, in which four family members in two generations had tri-allelic D7S820 genotype 10-11-12 and one family member had an abnormal bi-allele genotype 10-11. All of the four tri-allelic cases had the genotype 10-11-12, probably due to three copies of the D7S820 STR sequence in all cells (Type 2 tri-allelic pattern), and deduced alleles 10-11 were a linked inheritance in this family.