Genetic Genealogy Using Y-STR Markers in Conjunction with Reverse Parentage Testing Aid Efforts in Human Identification and Familial Search Investigation (Case Study)

Usha Rani M, Mahalakshmi N*, Thilaga D and Jeevanathan A

DNA Division, Forensic Sciences Department, Chennai, India *Corresponding author: Dr Mahalakshmi N, DNA Division, Forensic Sciences Department, Chennai-600004, Tamilnadu, India, Email: mahaforensic@gmail.com; musharani.2007@ rediffmail.com

Case Report

In the year 2015, an Indian Coast Guard Dornier aircraft was tasked for Maritime Surveillance and reconnaissance sortie on naval mission. The aircraft was launched at 1805 hrs from an airfield for a 4 hours duration sortie and scheduled to land back at the airfield at 2200 hours. The aircraft was declared overdue as it did not return to base till 2230 hours and search was initiated. Preliminary investigations revealed that the aircraft had last communicated with ATC Radio at 2100 hours on its return to the airfield. During the communication, the aircraft had intimated ATC of their intention of returning to the airfield at 2200 hours estimated arrival time. Subsequently, the radar contact of the aircraft was lost at about 2125 hours .It is further submitted that the aircraft were manned by three coast guard officers who have also gone missing along with the aircraft. One month later, wreckage of above flight was found at the length of 990 meters with the help of Reliance vessel Olympic canyon which included data recorder, two engines, propellers, and airframe parts etc. The remotely operation vehicle that has been carrying out underwater searches also found remains under sea and were retrieved from seabed. The remains were subjected to DNA analysis involving Y-chromosome testing and reverse paternity testing for victim identification and familial search investigation.

Results and Discussion

DNA analysis is a gold standard for identifying disaster victims. It is the main method of choice to identify individual disaster victims from severely fragmented, decomposed or skeletonized bodies [1]. It is one of the primary techniques to identify missing persons in a disaster, as defined by the Interpol Disaster Victim Identification Guide [2]. New innovations in DNA technology has made DNA analysis to be carried out in very small amounts of available DNA and in short duration of time. Vagish kumar, et al. [1] has demonstrated that DNA analysis significantly aids in the identification of mass-disaster victims.

Genetic characteristics on the human Y chromosome provide a lineage marker in the form of a single haplotype transferred directly from father to son. A haplotype is the set of STR alleles typed on a single Y chromosome. The uniparental nature of this marker has made the Y chromosome, a popular marker in genetic genealogy. Its popularity is based on its haploid character and its close association with the patrilineage behaviour [3]. Y-chromosome analysis and its implication in genealogical familial search investigation have undergone rapid improvements in recent years [4]. Because STR haplotypes are shared between paternally related men belonging to the same paternal lineage, Y STR haplotype analysis is employed in paternity disputes of male offspring and other types of paternal kinship testing, missing persons and disaster victim identification involving men [5].

Reverse parentage testing is also of high value in identification of remains as part of missing person’s investigations or mass disaster victim identification work [6]. In this testing, the question under consideration may be whether or not a child belongs to the mother and father tested or other biological reference available. This is essentially the opposite as that asked in parentage testing, namely given a child’s genotype who the parents are. Hence this testing was used in the present case to identify remains retrieved from seabed.

Disaster victim identification is very important for legal, administration and humanity reasons. DNA analysis is an important method of disaster victim identification particularly when other methods of identification are not possible or not conclusive [1]. Identification of the skeletal remains were quite challenging in this case. By the very nature of the disaster, there is typically damage done to the biological samples and hence the DNA molecules contained therein. Extreme environmental conditions both during and after the disaster impact the quality of the recovered skeletal remains. Hence the study samples which were in different states of degradation were subjected to different techniques and various types of protocols to generate amelogenein, autosomal STR and Y-STR profiles. These profiles were compared and analyzed by Y-STR and reverse parentage testing with the profiles generated from blood samples from living blood relatives of the victims.

In an individual, under each of the STR locus, one allele should be contributed by the biological mother (maternal) and the other allele should be contributed by the biological father (paternal). Of the two alleles under each of the 15 STR loci found in the deceased person 1, to whom the bones in item 1, item 4 (1-5 and 7-9) and item 6 (1 and 2) belong, one of the alleles is found to be present in Mr.A, the admitted father of the deceased person 1. Hence Mr.A is not found excluded from the paternity of the deceased person to whom the bones in item 1, item 4 (1-5 and 7-9) and item 6 (1 and 2) belong under any of the 15 STR loci tested. Also, the Y-STR haplotype detected in Mr.A and bones in item 1, item 4 (1-5 and 7-9) and item 6(1 and 2) have identical alleles under all the 17 Y-STR loci tested indicating the same family lineage (Table 1 and 2).

Similarly, of the two alleles under each of the 15 STR loci found in the deceased person 2, to whom the bone in item 3 belong, one allele was contributed by Mr.C and the other allele was contributed by Mrs.D, the admitted parents of the deceased person 2. Apart from the alleles accounted as present either in Mr.C or Mrs.D, no other unaccounted allele is present in the person to whom the bone piece in item 3 belongs. Hence Mr.C and Mrs.D are not found excluded from the paternity/maternity of the deceased person to whom the bone in item 3 belong under any of the 15 STR loci tested. Also, the haplotype detected in Mr.C and bones in item 3 have identical alleles indicating the same family lineage (Table 1 and 2).

Of the two alleles under each of the 15 STR loci found in the deceased person 3, to whom the bone in item 7 belong, one allele was contributed by Mr.E and the other allele was contributed by Mrs.F, the admitted parents of the deceased person 3. Apart from the alleles accounted as present either in Mr.E or Mrs.F, no other unaccounted allele is present in the person to whom the bone piece in item 7 belongs. Hence Mr.E and Mrs.F are not found excluded from the paternity/ maternity of the deceased person to whom the bone in item 7 belong under any of the 15 STR loci tested. Also, the 17 Y-STR haplotype detected in Mr.E and bone in item 7 have identical alleles indicating the same family lineage (Table 1 and 2).

DNA typing results of the skeletal remains and the blood samples collected from living blood relatives of the deceased victims demonstrated that 1) a) The deceased person 1 to whom the bones in item 1, item 4 (1-5 and 7-9), and item 6 (1 and 2) belong was the biological son of Mr.A. b) Mr.A and the deceased person 1 to whom the bones in item 1, item 4 (1-5 and 7-9), and item 6 (1 and 2) belong, come under the same family lineage. 2) a) The deceased person 2 to whom the bone in item 3 belong was the biological son of Mr.C and Mrs.D. b) Mr.C and the deceased person 2 to whom the bone in item 3 belong come under the same family lineage. 3) a) The deceased person 3 to whom the bone in item 7 belong was the biological son of Mr.E and Mrs.F. b) Mr.E and the deceased person 3 to whom the bone in item 7 belong, come under the same family lineage. The DNA extracted from item 2, item 4 (6), item 5 and item 8 could not be amplified and hence no DNA profile could be obtained.

Hence during identification of mass disaster victims, care has to be taken to collect and preserve body tissues for DNA extraction, since DNA begins to degrade and this degradation can be accelerated by environmental factors. Care should be taken to immediately preserve the collected DNA samples with available preservation methods and the collected samples should be processed as soon as possible. Utmost care should be taken not to contaminate the DNA samples. DNA analysis which was carried out on all the victim body and fragments enabled us to identify all the victims; one of the victims was identified with only a very small bone, thanks to our tireless efforts.

Conclusion

Genealogical studies using Y-chromosome STR markers and reverse parentage testing helped in the identification of victims. Chromosome Y testing also played immense role in aiding familial searching efforts by helping to screen out adventitious matches due to autosomal allele sharing. Victim identification is important considering humanitarian, legal and administrative aspects. Identification of victims based on our DNA report helped to inform the legal next of kin, resolve property issues, for criminal/civil litigation and for issuing of death certificates enabling the family to collect on life insurance policies. Also, the family members were able to get the remains to provide a proper burial and memorial service for their beloved ones. Hence DNA analysis should be considered and planned in every disaster incident. Apart from taking into consideration all the precautionary steps for DNA analysis, it must be ensured that all the victim body and fragments are subjected to DNA examination to hope for the identification of all the victims.

Acknowledgement

The authors thank Forensic Science Department, Chennai for the support and encouragement.