A Cross-Sectional Assessment of Quantitative Epidermal Melanin and Erythema Indices among North Indians.

Background: Remarkable diversity of skin tones among Indians ranging from pale pinkish to dark brown appears to be an ideal choice for the assessment of skin pigment variation. Aim: The present study was designed to assess the variation observed in melanin and erythema indices among north Indians. Material and Methods: Skin reflectance data (n = 574) was collected from six diverse populations of north India using DermaSpectrometer (DSM II ColorMeter) followed by statistical analysis to investigate the impact of geographical location and gender on constitutive skin pigmentation. Results: The melanin index (MI) varied between 17.93 and 56.92 (Mean (M) = 35.80 ± 6.26) whereas the erythema index (EI) varied between 4.92 and 18.82 (M = 10.48 ± 2.68). MI and EI of females were found to be significantly lower than males (P < 0.001). Geographical location exhibited a significant association with MI and EI (P < 0.001). Furthermore, we have noted a positive correlation between MI and EI (P < 0.001). Conclusion: The study has refined our understanding of skin pigmentation variation among north Indians in terms of significant association with geographical location {MI: F (5,568) = 31.07, P < 0.001; EI: F (5,568) = 73.37, P < 0.001} and gender {MI: t (386) = -4.06, P < 0.001; EI: t (386) = -11.96, P < 0.001} and rendered opportunities for further studies.

Investigating the morphology and genetics of scalp and facial hair characteristics for phenotype prediction.

Microscopic traits and ultrastructure of hair such as cross-sectional shape, pigmentation, curvature, and internal structure help determine the level of variations between and across human populations. Apart from cosmetics and anthropological applications, such as determining species, somatic origin (body area), and biogeographic ancestry, the evidential value of hair has increased with rapid progression in the area of forensic DNA phenotyping (FDP). Individuals differ in the features of their scalp hair (greying, shape, colour, balding, thickness, and density) and facial hair (eyebrow thickness, monobrow, and beard thickness) features. Scalp and facial hair characteristics are genetically controlled and lead to visible inter-individual variations within and among populations of various ethnic origins. Hence, these characteristics can be exploited and made more inclusive in FDP, thereby leading to more comprehensive, accurate, and robust prediction models for forensic purposes. The present article focuses on understanding the genetics of scalp and facial hair characteristics with the goal to develop a more inclusive approach to better understand hair biology by integrating hair microscopy with genetics for genotype-phenotype correlation research.

Forensic DNA phenotyping: Inferring phenotypic traits from crime scene DNA.

INTRODUCTION: Forensic DNA Phenotyping (FDP) has provided better understanding of various phenotypic features (e.g., height, skin colour, eye colour, structure and shape of scalp hair, baldness, facial features etc.) and associated genetic variations. The current study was designed to investigate the genetic variants and their potential contribution towards accurate phenotype prediction systems. Short Tandem Repeat (STR) based DNA typing method can be uninformative or with little potential to solve a crime in absence of suspect DNA profile in the database. Forensic DNA Phenotyping (FDP), prediction of externally visible characteristics (EVCs) from the crime scene DNA would certainly provide a new dimension to personal identification. The aim of this review paper is to highlight the significance and future prospects of FDP. RESULTS: A comprehensive literature review was conducted using PubMed and similar e-databases with keywords from two main components-phenotype and the associated genetic variants. To ensure a thorough literature review, searches were extended using the snowballing technique from reference lists. Key data extracted were type of study, sample characteristics (sample size, age, geographical location and ancestry), details of SNPs studied and prediction accuracies. CONCLUSION: Phenotyping tools based on genotyping and statistical analysis for the prediction of human pigmentation are propitious in solving cold cases. This indicates the inevitability of future studies for the identification of new genetic markers for accurate prediction of phenotype or EVCs via genome-wide association study (GWAS) in diverse global populations.