The first gene mapping investigation on human scalp hair whorls demonstrates both the genetic foundation and the polygenic nature of hair whorl orientation.
According to a publication in the Elsevier-distributed Journal of Investigative Dermatology, four related genetic variations that are probably to affect hair whorl orientation have been found.
A patch of hair that grows in a circular manner around a point determined by the orientations of the hair follicles is known as a hair whorl. The whorl number (single or double whorl) and whorl direction serve as typical descriptors of the scalp hair whorl pattern, a plainly observable human feature.
Understanding the genetic basis of whorl patterns may aid in unravelling significant biological processes since unusual whorl patterns have been seen in people with impaired brain development.
A replication research was conducted in 1,950 Chinese participants from the Taizhou Longitudinal research cohort after the initial genome-wide association study (GWAS) on human scalp hair whorls was conducted in 2,149 Chinese participants from the National Survey of Physical Traits cohort.
Lead investigator Sijia Wang, PhD, Shanghai Institute of Nutrition and Health, explained, "We know very little about why we look like we do. Our group has been looking for the genes underlying various interesting traits of physical appearance, including fingerprint patterns, eyebrow thickness, earlobe shape and hair curliness. Hair whorl is one of the traits that we were curious about. The prevailing opinion was that hair whorl direction is controlled by a single gene, exhibiting Mendelian inheritance. However, our results demonstrate that direction is influenced by the cumulative effects of multiple genes, suggesting a polygenic inheritance."
Four related genetic variations are found in the research (at 7p21.3, 5q33.2, 7q33, and 14q32.13). By controlling the cell polarity of hair follicles, these genetic variations are expected to affect the orientation of the hair whorls. Closure and expansion of the cranial neural tube may also be affected.
Professor Wang continued, "While previous work proposed the hypothesis of associations between hair whorl patterns and abnormal neurological development, no significant genetic associations were observed between hair whorl direction and behavioral, cognitive, or neurological phenotypes. Although we still know very little about why we look like we do, we are confident that curiosity will eventually drive us to the answers."
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