CASE REPORT

Brother-sister incest paternity case with the sametri-allelic pattern of parents at D3S1358 locus: a tetra-allelicbaby?

Kemal Murat Canturk & Ramazan Emre & Omer Muslumanoglu &

Agah Serkan Huner & Hakan Uygun & Arif Bingöl &Hüseyin Yavuz Aksoy & Kubilay Kınoglu

Received: 21 January 2014 /Accepted: 6 March 2014# Springer-Verlag Berlin Heidelberg 2014

Introduction

Tri-allelic patterns are genotyping irregularities which can beencountered during routine short tandem repeat (STR) profil-ing in forensic genetic laboratories. Tri-allelic patterns can beclassified into two types based on the relative fluorescentintensities of their three component alleles [1]. In the type 1pattern, the component alleles have unequal fluorescent inten-sity, whereas in the type 2 pattern, all three alleles have nearlyequal fluorescent intensity in the STR analysis [1]. The type 1pattern mostly results from somatic mutation of one allelewhich occurs during embryological development that resultsin a chimera with some cells containing the original allele andothers containing the mutant allele [2]. The type 2 pattern isusually caused by a localized duplication event or chromo-somal aneuploidy [1, 2].

Incest relationships usually refer to intrafamilial sexualabuse with clinical, social, and legal relevance [3]. Althoughfather-daughter incest is the most common one, incest alsoinvolves other family members such as brothers and sisters[4]. In our case, a 17-year-old teenager gave birth in a hospitaltoilet. She testified that she had been raped repeatedly by her20-year-old brother for 2 years. In this study, we report theDNA profiles of this brother-sister incest paternity case in

which the parents have the same tri-allelic pattern at theD3S1358 locus, and a tetra-allelic baby was born from thisrelationship.

Methods

Genomic DNA was extracted from the blood samples of themother, the alleged father, and the newborn baby usingBioRobot Universal System (Qiagen) and quantified usingQuantifiler Duo DNA Quantification Kit (AppliedBiosystems). AmpFISTR Identifiler kit (Applied Biosystems)was used to amplify microsatellite STR markers including theD3S1358 locus. The amplified products were analyzed using anABI 3130 genetic analyzer (Applied Biosystems) followed bydata analysis using GeneMapper v3.5 software. DNA typinganalysis of all the family members was confirmed usingInvestigatorESSplex kit (Qiagen).

Results

Table 1 shows the DNA profiles of the father, the mother, andthe baby, which were detected using AmpFISTR Identifiler kit(Applied Biosystems) (electroforeogram appearances of fam-ily members are given in Online Resource 1). We couldconfirm with a certainty of 99.99 % that the brother was thebiological father of the baby. We also confirmed the resultsusing InvestigatorESSplex kit (Qiagen) (Online Resource 2).Calculated data of the two commercial kits suggested thatpaternity could be proved with the probability of 99.99 % bythe analysis of amelogenin and 14 STR loci (the D3S1358

Electronic supplementary material The online version of this article(doi:10.1007/s00414-014-0984-2) contains supplementary material,which is available to authorized users.

K. M. Canturk (*) :R. Emre :O. Muslumanoglu :A. S. Huner :H. Uygun :A. Bingöl :H. Y. Aksoy :K. KınogluDepartment of Biology, Council of Forensic Medicine,Ministry of Justice, Istanbul, Turkeye-mail: drmuratcanturk@yahoo.com

Int J Legal MedDOI 10.1007/s00414-014-0984-2

locus excluded) even in our brother-sister incest case. Both themother and father belonged to the type 2 tri-allelic pattern,with three similar peak heights at the D3S1358 locus(Fig. 1a, b). The baby had only 17, 18 alleles at theD3S1358 locus (Fig. 1c) in the green dye of AmpFISTRIdentifiler kit (Applied Biosystems). These alleles interesting-ly had a similar peak height (3,179 and 3,298 relative fluores-cence units (RFU), respectively) compared to the other 10homozygote alleles at the THO1 locus (3,361 RFU) of thebaby in the green dye of AmpFISTR Identifiler kit (AppliedBiosystems) (Fig. 1c). Besides this, the sum of peak heightvalues of heterozygote alleles (2,217+1,381=3,598 RFU forD13S317, 1,646+1,651=3,297 RFU for D16S539,1,341+1,087=2,428 RFU for D2S1338) is similar to that ofonly one allele at the D3S1358 locus of the baby (3,179 and3,298 RFU) (Fig. 1c). So, these findings suggested thatthe baby had a tetra-allelic 17, 18, 17, 18 pattern at theD3S1358 locus.

Discussion

Forensic genetic practitioners are recommended to be awareof the possibility of some rare events to prevent misinterpre-tation of these cases. In this study, we reported the DNA

profile of a tetra-allelic baby of a brother-sister incest case inwhich both the parents have the same tri-allelic pattern at theD3S1358 locus. To our knowledge, this is the first represen-tation of a brother-sister incest case in which the parents havethe same tri-allelic 16, 17, 18 pattern at the D3S1358 locus.Previously, only one 16, 17, 18 tri-allelic pattern was reportedin a convicted offender sample at the Short Tandem RepeatDNA Internet Database (STRBase) (http://www.cstl.nist.gov/biotech/Strbase/var_D3S1358.htm#Tri).

Vidal and Cassar reported another case of a tri-allelicpattern at locus D3S1358 on chromosome 3p21 inheritedfrom a paternal grandmother; however, the tri-allelic patternsin their case were not the same when compared to our study[5]. Currently, 285 patterns of tri-allelic variants of autosomalSTRs have been reported on the STRBase (http://www.cstl.nist.gov/biotech/Strbase/var_D3S1358.htm#Tri). D18S51and FGA have been reported to have the highest frequencies(35 in 285) of tri-allelic patterns in the In our case, both thefather and mother have the same 16, 17, 18 tri-allelic pattern atthe D3S1358 locus, and this locus’s tri-allelic frequency is 11in 285 in the STRBase (http://www.cstl.nist.gov/biotech/Strbase/var_D3S1358.htm#Tri).

The extra alleles observed in our case were type 2 alleles,since they had similar peak heights to those of the other twoalleles (Fig. 1a, b). Additionally, other loci of the family haveone allele or maximum two alleles, so aneuploidy and con-tamination were ruled out. These findings suggest that a tri-allelic pattern may result from a localized duplication eventrather than somatic mutation or aneuploidy or contamination.

The baby had only 17, 18 alleles on the D3S1358 locus,and these alleles interestingly had similar peak heights com-pared to the other 10 alleles of the THO1 locus of the baby(Fig. 1c) in the green dye of AmpFISTR Identifiler kit(Applied Biosystems). Furthermore, the sum of peak heightvalues of the other heterozygote alleles was similar to that ofonly one allele at the D3S1358 locus of the baby (Fig. 1c).Therefore, peak height data suggested that the baby had atetra-allelic 17, 18, 17, 18 pattern at the D3S1358 locus. Toour knowledge, a tetra-allelic 17, 18, 17, 18 pattern at theD3S1358 locus has not been reported in the literature. Wefound compatible results using InvestigatorESSplex kit(Qiagen) (Online Resource 2). Paternity analysis results wereconsidered as sufficient for the judicial officers, and furtheranalyses were denied.

Interpretation of STR results can be difficult in paternitytests of close relatives since more alleles are usually sharedbetween close genetic relatives, as well as abnormal geneticvariations can be encountered. Thus, forensic specialists haveto be more cautious in the interpretation of STR results ofincest cases.

Table 1 DNA typing results of the father, mother, and baby studied usingAmpFISTR Identifiler kit (Applied Biosystems)

Locus Father Mother Baby

D8S1179 13-14a 12a-13 12-14

D21S11 30a-30.2 28a-30 28-30

D7S820 10-10a 8-10a 10-10

CSF1PO 12a-13 12-12a 12-12

D3S1358 16-17a-18a 16-17a-18a 17-18b

THO1 8-10a 6-10a 10-10

D13S317 11-11a 8a-11 8-11

D16S539 8a-11 11-12a 8-12

D2S1338 23a-25 22a-25 22-23

D19S433 14-15.2a 14-15.2a 15.2-15.2

VWA 17-19a 14a-17 14-19

TPOX 9-11a 9-11a 11-11

D18S51 14-14a 14-14a 14-14

Amelogenin X-Ya X-Xa X-Y

D5S818 10a-12 12a-13 10-12

FGA 21-24a 19-23a 23-24

a Transmitted alleles from the father and mother to the babyb This locus exhibited a di-allelic pattern consistent with two copies of the“17” allele and two copies of the other “18” allele

Int J Legal Med

References

1. Clayton TM, Guest JL, Urquhart AJ, Gill PD (2004) A genetic basisfor anomalous band patterns encountered during DNA STR profiling.J Forensic Sci 49:1207–14

2. Rolf B, Wiegand P, Brinkmann B (2002) Somatic mutations at STRloci—a reason for three-allele pattern and mosaicism. Forensic Sci Int126:200–2

3. Gunduz T, Karbeyaz K, Ayranci U (2011) Evaluation of the adjudi-cated incest cases in Turkey: difficulties in notification of incestuousrelationships. J Forensic Sci 56(2):438–43. doi:10.1111/j.1556-4029.2010.01662.x

4. Celbis O, Ozcan ME, Ozdemir B (2006) Paternal and sibling incest: acase report. J Clin Forensic Med 13(1):37–40

5. Vidal C, CassarM (2008)A case of tri-allelic pattern at locus D3S1358on chromosome 3p21 inherited from paternal grandmother. ForensicSci Int Genet 2(4):372–5. doi:10.1016/j.fsigen.06.002

Fig. 1 Green dye channel of AmpFISTR Identifiler kit containing theD3S1358 locus. Allele callings (upper numbers) and peak height values(lower numbers) are also represented under the signals. a, b The fatherand the mother’s 16, 17, 18 tri-allelic patterns at the D3S1358 locus,respectively. c The baby has only 17, 18 alleles at the D3S1358 locus, and

these alleles have similar peak height values to those of the neighboringhomozygote allele. The sum of peak height values of heterozygote allelesis similar to that of only one allele at theD3S1358 locus of the baby. Thus,this pattern suggested that the baby has a tetra-allelic 17, 18, 17, 18pattern at the D3S1358 locus. d Positive control

Int J Legal Med