Human skin pigmentation is a phenotypic trait that varies within a population or among different populations. In addition to the genetic factors, some of the diseases (may be genetic or epigenetic), exposure to UV or usage of cosmetics may also be involved in the pigmentation outlook. It is possible to predict human identity on the basis of DNA polymorphisms in the genes coding human phenotypic characteristics.
In case of human skin pigmentation various genes are responsible to code variability among which SLC24A5 is an important contributor. This area of research is important in the field of forensic science in cases where reference samples are not available for comparison with the DNA profiles obtained from the crime scene evidence. SNPs in the coding region of exon3 (84bp) of SLC24A5 related to skin pigmentation (as reported in literature) are associated to a predictable variation in skin color in Pakistani Population.
Blood samples (62) were collected from the participants having three types of skin coloration fair= 20, medium=22 and dark=20 from general population belonging to Punjab. Organic method (Phenol chloroform extraction method) of DNA extraction was used. After extraction DNA was quantified on nanodrop spectrophotometer. Primers for the exonic region 3 of SLC24A5 gene were designed using primer 3 software. PCR amplification of the selected region was done through touch down PCR. DNA after obtaining PCR products was purified and the samples were sequenced bi directionally on ABI 3130XL Genetic analyzer.
The results of sequencing were analyzed using CHROMAS Lite 2.1 software. Sequence was converted into Fasta Format required for alignment study. Alignment tools like Blast were required for SNPs identification and comparison of all the sample sequences with the reference sequence. Mean color scores and mean ages of all the skin color groups were calculated separately in both male and female participants. Two types of genotypes were observed i.e, AA and AG. 24 out of the total sample size showed heterozygous peaks and confirmed the polymorphism also in Pakistani population at position 299 of the sequence. Difference between allelic and genotype frequency of studied gene were evaluated and by t test and association analysis to check out the significance of the studied data with the skin coloration was done and it was concluded that AA genotype is significantly associated with fair skin color in male and female population. Furthermore, AG genotype was significantly associated with dark skin coloration in female population. This type of study reveals that after the genetic analysis of the DNA obtained from the crime scene, prediction of skin color/hue of crime related individuals of fair skin color as well as dark skin color belonging to Pakistani Population can be made in those cases where reference samples are not available. So this can be used as a genotypic marker for screening out and forensic identification of individuals in various crime cases where reference samples are not available for comparison purposes and matching suspects.