Paternally inherited trisomy at D21S11 and mutation at DXS10135 microsatellite marker in a case of fetus paternity establishment

The case of establishment of paternity of an aborted fetus was examined with 15 autosomal STR markers. The genotype of the fetus was X at amelogenin marker and showed inheritance of both the alleles of father at D21S11 marker, thus displaying unusual tri-allelic pattern. The cases where mutation in any of biparental autosomal STR markers is observed, the use of additional STR marker system is recommended. On testing all the three samples with 12 X-STR markers, all the maternal and paternal alleles were accounted in the female fetus except at DXS10135 marker. The genotypes of mother, fetus and father at DXS10135 were 20, 22; 20, 20 and 21, which confirmed mutation of the paternal allele in the female fetus. The paternal allele contracted from 21 to 20. The allele peak heights of D21S11 and DXS10135 markers were also examined to rule out the possibility of any false allele. The probability of paternity was 0.99999999, which confirmed the paternity of the fetus. This paper presents unusual occurrence of mutation observed with two multiplex STR systems, with AmpflSTR identifier plus Kit (Applied Biosystems, Foster City, CA) and Investigator Argus X-12 multiplex kit (Qiagen, Germany), thus suggesting forensic DNA experts on high alert while interpreting the DNA test results.