Externally visible characteristics (EVCs) are the phenotypic characters of an individual such as body height, pigmentation (skin, eye and hair color) and facial features (eye shape, lip size, nose shape etc. EVCs are multifactorial complex traits and it is the interaction of several genes among themselves and the environment that define the phenotype. DNA phenotyping is the use of genetic information such as DNA to determine a phenotype. It helps forensic investigator to predict the physical appearance of an individual to find unknown perpetrators or to identify missing persons using molecular analyses from biological samples in cases where all other means of inquiry, including conventional DNA profiling are non-informative.
Genome-wide association studies, linkage analyses, candidate gene studies, animal (knock-out) studies and evolutionary genetic studies resulted in the identification of a number of DNA markers that are associated with human appearance characteristics. These studies identified many single nucleotide polymorphisms (SNPs) within DNA markers and adjacent DNA sequences, which are associated with variation in human appearance characteristics. By using PCR and SNP genotyping, SNPs associated with variation in human appearance characteristics can be used for human appearance predictions. Our study is aimed at establishment of hypothesis that variation in the 3'-UTR region of HMGA2 genes associated with the variations of height as an externally visible characteristics. Height is a classical polygenic trait that has provided general insights into the genetic architecture of common human traits. Human adult height is an important physical index to reflect the processes of growth and development. As a classic, polygenic quantitative trait, adult height is under strong genetic influence with heritability estimated up to 90%. HMGA2 is one of the major determinants of height and thus can be used as genetic marker for forensic identification.
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In this study blood samples were collected from 30 males and 30 females categorized according to tall, average and short heights. A total of ten individuals were selected for each category. DNA of these individuals were extracted using organic extraction method. Extracted DNA was amplified using PCR with primers designed against 3'-UTR region of HMGA2 through Primer 3 software. Amplicons of 232 bp were sequenced by using Genetic analyser. CLUSTAL-W was used for sequence alignment that helps in identification of rs1042725 polymorphism in the 3'-UTR region of HMGA2 gene and other possible SNP‟s. Rs1042725 polymorphism in the 3'-UTR region of HMGA2 gene is marked by transition from C to T. Observed genotypic and allelic frequencies of tall, average and short heighted male and female was calculated and these genotypic and allelic frequencies were compared between different height ranges of male and female categories. Genotypic frequencies among the males were 0.03 for the CC genotype, 0.17 for the TT genotype and 0.8 for the CT genotype whereas genotypic frequencies among the females were 0.2 for the CC genotype, 0.36 for the TT genotype and 0.43 for the CT genotype. Allelic frequencies among the male were 0.43 for the C allele and 0.56 for the T allele whereas females have 0.42 for the C allele and 0.58 for the T allele. Genotypic frequencies among the tall males were 0 for the CC genotype, 0.2 for the TT genotype and 0.8 for the CT genotype whereas genotypic frequencies among the tall females were 0.2 for the CC genotype, 0.5 for the TT genotype and 0.3 for the CT genotype. Allelic frequencies among the tall male were 0.4 for the C allele and 0.6 for the T allele whereas tall females have 0.35 for the C allele and 0.65 for the T allele. Genotypic frequencies among the average males were 0 for the CC genotype, 0.2 for the TT genotype and 0.8 for the CT genotype whereas genotypic frequencies among the average females were 0.2 for the CC genotype, 0.2 for the TT genotype and 0.6 for the CT genotype. Allelic frequencies among the average heighted males were 0.4 for the C allele and 0.6 for the T allele whereas average females have 0.5 for the C allele and 0.5 for the T allele.
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Genotypic frequencies among the short heighted males were 0.1 for CC genotype, 0.1 for the TT genotype and 0.8 for CT genotype whereas genotypic frequencies among the small females were 0.2 for the CC genotype, 0.4 for the TT genotype and 0.4 for the CT genotype. Allelic frequencies among the short heighted males were 0.5 for the C allele and 0.5 for the T allele whereas short heighted females have 0.4 for the C allele and 0.6 for the T allele. Genotypic and allelic frequencies among the tall, average and short heighted males and females were non-significant according to T-test at P-value (0.5) and level of significance (0.05). Also, by applying Chi square test it is concluded that there is no significant association of particular genotype with specific category of category of height group. Stastical analysis shows 0.67 P value which is greater than level of significance 0.05
Our study results were different with the study of (Hendriks et al., 2011) according to his study an rs1042725 single nucleotide polymorphism has been reported to be associated with the increase in the height amongst the individuals. Their study revealed that those individuals that carried the CC allele were tallest as compared to the individuals having the TT allele (Hendriks et al., 2011). Research to unravel the genetic basis of height , studies with many large sample groups from different parts of the world and prediction possibilities are recommended to develop an application for predicting human height on the basis of DNA.