Short Tandem Repeat Typing Using Endogenous DNA Isolated from Human Fingernail

Abstract

Genomic DNA was isolated from variable biological sources. Nails contain genomic DNA but there is limitation in isolating of genetic material from this tissue due to the special composition and structure of this tissue in which DNA embedded in keratinized cells. This study aimed to investigate the capability of using DNA that isolated from fingernails in forensic analysis. Thirty fingernails clipping were collected from three groups (10 fingernail samples for children, 10 fingernail samples for adolescent and 10 fingernail samples for adult) in addition to thirty buccal swabs collected from the same volunteers as reference samples. Both fingernail clipping and buccal swabs were subjected to DNA extraction using phenol/chloroform extraction. All samples were typed for fifteen autosomal STR loci along with amelogenin, using the Applied Biosystems AmpFiSTR® IdentifilerTM kit. Our finding showed that input of 5 mg nail material (1 to 2 of fingernail clippings) gives a variable yield of DNA concentration also there was no significant difference in The mean of concentration for samples that isolated from whole fingernail and those isolated from fingernail after cut into small pieces for children groups while there were significant difference for adult and adolescent groups (0.107702, 0.07544 and 0.000192 respectively). Also the allele’s percentage of STR profiles for three age groups was fluctuated among (100, 33.3, 53.3, 66.6, 73.3, 86.6, and 93.3%). [DOI: 10.22401/JUNS.21.1.16] Keyword: Genomic DNA, Fingernail, DNA analysis, Allele percentage, STR profile. Introduction Deoxyribonucleic acid (DNA) profiling is an effective technique for human identification and/ or the resolution of criminal and civil legal disputes. One force characteristic of DNA profiling is that it may be used in assortment of various biological sources. Some of these sources include blood [1,2], semen[3], hair[4-6], saliva[7],bone[8-14] and teeth [1517]. DNA profiling of individuals with short tandem repeat (STR) markers is commonly used in forensic genetics and paternity testing. Short tandem repeats are non-coding regions of DNA used for forensic identification due to the variation between individual found in these regions [18]. They occupy about 3% of the human genome and occur on every 10,000 nucleotides [19]. Nail, hair, horn and feather (keratinous tissues) have been utilized as a source of genetic material for over 20 years. There are particular benefits of using keratinous tissues include the ease obtaining of the sample and the relative stability of DNA in these tissues [20]. Many studies have confirmed that nails are suitable for analysis [21-23], but their use as a provenance of DNA in the forensic field is rather rare. The aim of the present study was to verify whether human nails are appropriate for personal identification and paternity testing. Materials and Methods Samples Thirty fresh human fingernails were obtained from random volunteers an age average (8-60). Thirty buccal swabs were also collected from same volunteers and used as reference samples. Fingernails were subjected to two different treatments. In the first treatment DNA was isolated from whole fingernail clipping while in the second treatment fingernail clipping was cut into small pieces to increase surface area exposed to lysis solution. DNA Extraction DNA was extracted from fingernail samples using organically after a modification of a previously published protocol [21] and buccal swab samples were extracted according to Souvik et.al. 2013 [24]. To remove the